Irrigation Terminology
The following terms and definitions are generally accepted as standards
within the irrigation industry, regardless of state or region. Reference
materials include, but are not limited to, the Irrigation Association,
Webster’s New World Dictionary, Febco, the Turf Irrigation Manual, the
American Water Works Association (AWWA ), Netafim, Toro, Rain Bird,
the Texas ET web site, and the Texas Commission on Environmental Quality
(TCEQ). These definitions and references do not displace an original
definition or reference.
Absorption Rate – The rate (or speed) at which soil will accept water. The
speed at which water can penetrate or infiltrate the soil. Also called
percolation or infiltration rate. As the soil “capacity” is reached, the
absorption rate will decrease. It is affected by soil type, slope, run-off,
etc. Different soil types absorb water at different rates. For example,
sandy soil, which is very coarse, has the fastest absorption rate, while
clay soil has a slower absorption rate and the greatest horizontal
movement of water.
Active Root Zone – The depth of soil in which a plant extracts most of the
water it needs for evapotranspiration.
Actual Head Pressure – The operating pressure measured at the base of
a sprinkler head. Actual head pressure is calculated by deducting all
pressure losses from the static water pressure. Actual head pressure has
to be equal to, or greater than, the minimum head pressure, for a given
sprinkler head, to function correctly.
Actual Head Pressure = static pressure - all pressure losses
Air Gap – An approved air gap is the unobstructed vertical distance through
free atmosphere between the lowest point of a water supply outlet
and the flood level rim of the fixture or assembly into which the outlet
discharges. These vertical, physical separations must be at least twice
the diameter of the water supply outlet, but never less than 1 in. (25
mm).22 A common air gap would be that of a typical household sink in
which there is an air gap between the water in the sink and the faucet
above it.
Air/Vacuum Relief Valve – Small device used on some subsurface drip
irrigation that allows air into the dripperline when the system is not
running which eliminates any vacuum that could result in debris or
contaminants being sucked into the piping system.
CHAPTER TWCOHAP — CTEROMMON Two — LAND
Allowable Depletion (AD ) – The amount of water, in irrigation
management, that is allowed to be depleted from the plant available
water before an irrigation event is scheduled. Also referred to as
Managed Allowable Depletion (MAD ). Generally, 50% depletion is
the rule of thumb.
Alternating Current (AC) – An electric current that reverses it direction
periodically.
Anti-Siphon Device – Any device that introduces air into the system to
prevent “back siphonage”. Refer to the definitions for atmospheric
vacuum breaker or pressure-type vacuum breaker.
Application Rate – Rate at which water is applied by sprinkler heads in a
certain pattern. Usually measured in inches per hour, gallons per hour
or gallons per day. Commonly called “precipitation rate”. There are
three methods in which to evaluate application rates:
1. A densogram (see definition).
2. Precipitation rate formulas. For example, the following formula
for precipitation rate, the total area method, is one of several
precipitation formulas in chapter 5:
96.3 x Total GPM
Total area
3. A water audit. This is the most accurate method to evaluate
precipitation rates. You are actually collecting water (using
catchment devices) and measuring the actual application rate and
uniformity over a given area.
Aquifer – An underground layer of porous rock, sand, etc. containing water,
into which wells can be sunk.24
Arc – The surface area of the landscape to which a sprinkler head will provide
water. Usually described in degrees or part of a full circle (360
degrees) head. The degrees of coverage of
a sprinkler from one side of a pattern to the
other. For example, a 90-degree arc would be a
quarter circle sprinkler, a 180-degree arc would
be a half circle sprinkler, a 360-degree arc
would be a full circle sprinkler, etc.
Architect Scale – Scale expressing foot measurements in parts of an inch.
Example: 1/8” = 1’, 3/16” = 1’, 1/4” = 1’, etc.
As-Built Plan – A corrected or redrawn plan showing the “actual scaled”
location of all major components of the system and other information Landscape Terminology
the property owner might require. An as-built plan is an invaluable tool
for irrigators to locate major components at a later date. See definition
for “record drawing”.
Atmospheric Vacuum Breaker (AVB) – A backflow prevention device that
allows air into the piping system, with the use of a float that moves up and
down, to prevent backsiphonage. No back pressure can exist for proper
operation. It cannot be under constant pressure for more than 12 hours in
any 24-hour period. This device must be installed vertically and a minimum
of 6” higher than all down stream piping and the highest downstream
head or outlet. There cannot be any shut off valves downstream of the
AVB. A separate AVB must be installed on the discharge side of each
control valve, between the valve and all emission devices.
Automatic Control Valve – An electrical or hydraulic remote control valve
in a sprinkler system which is activated by an automatic controller. Also
called a section valve, circuit valve, zone valve, remote control valve,
electrical valve, or hydraulic valve.
Automatic System – An irrigation system which will automatically cycle
(water) according to a preset program.
Available Water – Water (measured in inch of water per inch of soil) that is
actually accessible for the plant to use.
AWWA – Abbreviation for American Water Works Association.
Backflow – An unwanted reversal of the flow of water in a piping system which
can potentially allow non-potable water to pollute or contaminate the
potable water supply. Caused by backpressure or backsiphonage.
Backpressure – Any condition that could create pressure in the discharge
(outlet or downstream) side of the piping system that is greater than
that of the supply (inlet or upstream) side of the system. Examples of
this occurrence would be pressure caused by gravity (due to elevation),
a pump installed on the system or steam and/or air pressure.
Backsiphonage – A form of backflow due to negative or sub-atmospheric
pressure within water system. A break in the city main line or a fire
department utilizing excessive water to fight a nearby fire could both
induce a backsiphonage.
Backflow Prevention Methods – Any approved device which prevents an
undesirable reversal of flow of water by the introduction of air, use of
check valves, or a combination of both principles. Examples include:
1. An Air Gap
2. An Atmospheric Vacuum Breaker (AVB)
3. A Pressure Vacuum Breaker ( PVB)
4. A Double Check Valve Assembly (DCA )— CTEROMMON Two — LANDS C
5. A Reduced Pressure Principle Device (RP)
Ball Driven Heads – Type of rotary sprinkler in which rotation is achieved by
a steel ball which is set into a circular motion by water passing through
the head.
Block (of heads) – A section of sprinklers controlled by one zone valve.
Body (of heads) – The exterior case or shell of the sprinkler.
Booster Pump – A pump which is installed in the water supply line and is
designed to raise the pressure in the irrigation system.
Bubblers – A type of sprinkler head designed to irrigate level and defined
shrub beds. It is mounted on a riser and puts out a very small umbrella-shaped
adjustable flow of water.
Bushing – The pipe fitting used to change an irrigation component to a larger
or smaller size
Capillary Action – The main effect distributing water horizontally through
the soil.
Catchment Devices – Containers that are used to collect measurable water in
order to conduct a water audit.
C-Factor – Rating of the smoothness of the inside of pipe. The higher the
C-Factor, the smoother the inside diameter of the pipe. PVC has a
C-Factor of 150, whereas copper is 140. Generally, the C-Factor
decreases over time indicating the pipe gets rougher, resulting in
increased friction loss.
Check Valve – A valve which permits water to flow in one direction only.
Class Pipe – A method by which PVC pipe is grouped according to the
working pressure. Pressure rated with a wall thickness in direct ratio
to the diameter. All sizes in that class have the same working pressure.
(Class 125, Class 160, Class 200, Class 315).
Contour Line – A line of equal elevation drawn on a plan. For example, a
contour line labeled “250” means that everywhere along that line is
250 feet above mean sea level. Contour lines are usually accurate to
+/- one-half of the contour interval; ie. when a contour interval of onefoot
is indicated on a plan, a particular contour line will be accurate to
+/- 6 inches.
Control Wires – The wires (from the automatic controller) which transmit
signals to the automatic electrical valves to open and close (see
direct burial wire).
Controller – An automatic timing device, which signals the automatic valves
to open or close according to the prescribed program. Because of
current technological advances, controllers have expanded from very
simple mechanical devices to very sophisticated central control units
that operate numerous satellite units in the field. Wireless automatic
systems are emerging and PC irrigation controller interface hardware
and software solutions are becoming the standard for city parks, golf
and commercial sites. ET -based controllers are becoming very popular.
These innovative controllers will schedule water events based on the
evapotranspiration (ET ) rates (see evapotranspiration). This technology
is becoming standard for the average residential sprinkler system.
Controllers are also referred to as “timers or clocks”.
Coupler Key – A bronze tube with a handle which inserts into a quick coupler
valve (and turned one quarter revolution) for supplemental water. May
be fitted with a sprinkler head, hose swivel or faucet. Also called a
“Quick Coupler Key”. See definition for “quick coupler valve”..
Coverage – The pattern of water that a certain sprinkler covers. Various
sprinklers or sprinkler nozzles have varying patterns of coverage: quarter,
half, full, etc. Most manufacturers even have adjustable arc nozzles that
suffice for many odd-shaped areas.
Cross Connection – Any actual or potential connection between a potable water
supply and any source of contamination or pollution.
Cycle – Refers to one complete operation of the controller through a watering
program.
Density Factor – Coefficient used to adjust the potential (or reference)
evapotranspiration to reflect the usage of water in relation to the
density of the planting.
Design Pressure – The sum total of the desired (or minimum) head pressure
added to the total of all pressure losses. A stated pressure indicating
the minimum pressure required for the system to operate properly. The
design pressure has to be equal to or less than the static pressure for
the system to work.
Design Pressure = Minimum Head Pressure + Total of all Pressure Losses
Desired Head Pressure – The manufacturer’s minimum recommended
operating pressure for a specific head. It is usually stated as the
minimum head pressure.
Densogram – Graphic representation of precipitation. Higher rates are
indicated by darker colors. These are used to check the amount of
precipitation and uniformity in a given irrigation area.
CHAPTER TWCOHAP — CTEROMMON Two — LANDS C
Diameter – Size or dimension of piping.
ID – Inside diameter
OD – Outside diameter
Diaphragm – That portion (flexible membrane) of an automatic valve which
regulates the passage of water through the valve.
Digital Multimeter (DMM ) – A meter (with a digital display) that measures
voltage, ohms and amps. Used in irrigation electrical troubleshooting.
Direct Burial Wire – Any wire approved for direct underground burial without
conduit. UL (underwriters laboratories) approved requires a minimum
insulator thickness of 4/64th”.
Direct Current (DC) – An electric current flowing in one direction.25
Distribution Curve (of a Sprinkler Head) – A curve showing the rate of water
application by a sprinkler at various points along the radius in inches
per hour.
Distribution Uniformity (DU) – The uniformity of the distribution of
water over a given irrigated area. The measure of how uniformly
water is made available to the landscape materials over an area.
DU is expressed as a percentage and generally represents the major
component of irrigation efficiency. It is calculated using a catchment
test. Divide the average reading of the driest 25% (lowest onequarter)
of catch cans by the average reading of all the catchments,
and then multiply by 100. Closer to 100% is better. A DU of 100%
would indicate the area (in question) would be receiving the same
amount of water. 75% - 80% is an excellent DU . 65% - 75% is
considered a good DU reading. Generally, rotary heads have a higher
uniformity than spray heads.
Double Check Valve Assembly (D.C.V.A.) – Backflow prevention
assembly, using two shut-off valves and two check valves assembled
and pre-tested at the factory, designed to physically block or prevent
the backflow of water. For non-health hazard conditions and the
protection of a pollutant only. It will protect against backpressure and
backsiphonage.
Drain Valve – An automatic or manual valve used to drain water from a line
after the system is through running to protect irrigation components
against freeze damage.
Drip Irrigation – The slow application (low volume) of water to the specific
root zone area of the plant material using very low pressure. Usually
expressed in GPH (gallons per hour).
Dry Line Shock (Dry Pipe Shock) – The shock which occurs when a valve is
opened and the water travels unrestricted in empty piping. Air in
the piping is quickly voided through heads at higher velocities than
normal. Unlike water, air is compressible, and can damage irrigation
components such as the heads and piping. It is suggested that (after
the initial installation) irrigators turn the system on slowly, allowing the
piping to gradually fill with water, in order to void most of the air and
minimize component damage.
Dual Programming – The feature on many newer automatic controllers
that allows two or more different watering schedules or programs. Also
called “Multiple Programming”.
Dynamic Water – Water that is in motion through the system. Also referred to
as “Working Pressure”.
Dynamic Pressure – The pressure of water when it is in motion. Also referred
to as “Working Pressure”.
Elevation Gain – Pressure gained as water is used downhill from its source. It
is figured at the rate of .433 pounds per square inch (psi) pressure gain
for each foot of elevation lost.
Elevation Lost – Pressure lost as water is used uphill from its source. Pressure
is lost at the rate of .433 psi for each foot of elevation gained.
Elevation gain or lost works similar to a car coasting up and down a hill.
When a car (already in motion) starts coasting uphill without applying
the throttle or brakes, it begins to lose power similar to water traveling
uphill which loses psi. A car coasting downhill will gain momentum,
similar to water traveling downhill in which it gains psi. However, the
gain or loss of psi of water is due to the weight of the water as a result
of its height above a given point.
Emitters – A small mechanical device (used in drip irrigation) to limit water
flow to a drip or slow trickle. Discharge rate is usually expressed in
gallons per hour rather than gallons per minute.
Engineer’s Scale – Scale expressing foot measurements as a given number of
feet per inch. Example 1” = 10’, 20’, 30’, etc.
Evaporation – The natural process of changing water into vapor.
Evapotranspiration (ET) – The combination of water that has evaporated
from the soil and transpired from the plant material. This is the
measurement of total amount of water needed for plants to grow (See
Evaporation and Transpiration).
Field Capacity – This is the amount of water the soil can retain after the soil
has been saturated and allowed sufficient drainage (usually several
days after a rainfall).
FIP – Abbreviation for “Female Iron Pipe”.
Flow – The movement of water in a piping system. This movement of the water
causes friction loss.
Flow Control Valve – A valve that can be adjusted mechanically to restrict
water flow. This can be referring to a main shut-off valve (such as a
gate or ball valve) or an automatic valve (electrical or hydraulic) which
may have a manual flow control.
Flow Restrictions – Physical restrictions in the irrigation system components
that affect the flow of water causing a pressure loss.
Flush Flow – The higher initial momentary flow through a drip or trickle system
required to flush emitters before pressure compensation occurs. In
drip irrigation systems, flush valves are a desirable, if not necessary,
component to keep lines free of debris.
Flush Valves – A necessary component in drip irrigation systems to keep
lines free of debris. Typically buried in a box with subsurface drip
application, a flush valve allows the velocity of water inside the drip line
to increase momentarily when the system is first turned on. This allows
debris to move out of the system through the flush valve.
Foot-Head “Feet of Head” – A measure of pressure equivalent to .433
pounds per square inch (psi) and equal to the weight of one vertical
foot of water on a one-square-inch surface. Example: a 100’ water
tower equals 100 feet of head or 43.3 psi (100 x .433).
FPS – The abbreviation for “feet per second”.
Friction Loss – Pressure loss due to friction as water flows through all
components (ie. meter, backflow device, zone valves, piping, etc.) of a
system. The rougher the inside surface of the pipe or component, the
more friction loss is encountered.
Gate Valve – Manual valve capable of permitting straight-through, fullopening
flow. These valves are typically used after the POC (point
of connection) and before the backflow device as a manual master
shut-off. Uses a wedge-type metal-to-metal gate or disk for restricting
partial flow. This valve is not recommended for frequent use in throttling
flow in an irrigation system due to the excessive wear on the metal-to metal
parts. To do so may cause leakage. A ball valve is another type
of valve that is preferred and serves the same purpose.
Gauge (Wire) – Standards used for wire sizing. The larger the gauge number,
the smaller the wire diameters. Sizing wire is similar to sizing piping.
The farther the distance, the more friction loss in water flow and more
resistance in wiring is encountered; hence, piping and wiring have to be
sized larger to account for these occurrences.
Gear Driven Heads – Type of rotary sprinkler that has a slower, constant
rotation that is achieved by water passing through a series of gears
within the head.
Globe Valve – A valve which uses a rubber or composition plug against the
valve body seat to restrict or stop the flow of water. Can be either
straight-through or angle configuration.
GPH – Abbreviation for “gallons per hour”. Used when working with lowvolume
irrigation systems such as with drip irrigation.
GPM – Abbreviation for “gallons per minute”, a standard measurement of
water flow.
Gray Water – Domestic wastewater, such as bath, sink, and washing machine
expulsion. It does not include toilet water containing human waste.
Hazard (Degree of) – A measure of the degree of risk or harm to the
public’s health; for example, the term is used to categorize an irrigation
system as a “non-health” or a “health hazard”. A pollutant is a
substance that may affect the color or odor of the water, but not create
a health hazard. This would be considered a low, or non-health hazard.
A contaminant is a substance that may cause illness or death if ingested.
If encountered, this would be classified as a health hazard. Any system
rated as a “health hazard” (such is the case if a fertilizer injector is
installed) must utilize a backflow prevention device requiring annual
testing by a licensed Backflow Prevention Assembly Tester.
Head Spacing – The spacing between sprinkler heads.
Head-to-Head Spacing – Spacing of heads that is equal to the published
radius of the head. This is also referred to as 50% spacing because it
is 50% of the diameter of the head.
CHAPTER TWCOHAP — CTEROMMON Two — LAN
Hydraulically Controlled – A system which uses water pressure through
tubing to operate remote control valves.
Hydraulics – The study of fluid while in motion or at rest. The mechanical
properties of water in motion, or at rest, and the calculation of pressure
losses and irrigation system requirements.
Hydrozone – An irrigation area encompassing plant material with similar
watering requirements due to environmental and/or geographic
influences including, but not limited to, soil type, slope, site orientation,
and solar radiation.
Hygroscopic Water – Water that is held tightly by the soil and inaccessible to
the plants.
Impact Head – A type of rotary sprinkler head that utilizes a driver arm
(mounted on the side) to create rotation.
Infiltration Rate – The speed at which the water can infiltrate the soil. Also
referred to as “Absorption Rate or Percolation Rate”.
In-Line Valve – The component that regulates (on command from the
controller) the on/off mode of the water from the main line to the
sprinkler heads. Also referred to as a remote control valve.
Insert Fitting – A fitting which fits inside the pipe or tubing. Usually used on
polyethylene pipe and tubing.
IPS – Abbreviation for “Iron Pipe Size”.
Irrigation Design – A plan showing graphic or dimensional location of the
components of an irrigation system; ie., sprinkler heads, piping, valves,
backflow prevention device, etc.
Irrigation System – The permanent assembly of irrigation components, such as
heads, valves, pipe, etc., to apply managed water to a given landscaped
area and/or for the purpose of dust reduction or erosion control.
Isolation Valve – An isolation valve, generally a gate or ball valve, serves
as a main shut-off device for the complete irrigation system as needed
for servicing or repair. It must be located between the meter and the
backflow device.
Landscape Irrigation – The art and management of applying water to the
landscape in a manner to encourage the growth of plant material and
support water conservation.
Landscape Coefficient – Coefficient used in adjusting the reference
evapotranspiration by species, density, and microclimate factors.
Lateral Piping – Piping between the remote control valve, not subject to
constant main line pressure, and the sprinkler heads.
LANDSCAPE IRRIGATION TERMINOLOG
Loop Main Line – A main line designed to provide water to any valve from
two or more directions. Using a looped main line greatly improves the
hydraulics.
Main Line – That portion of the irrigation piping normally under constant
pressure, located between the water source and remote control valves
or quick coupler valves. The main line is considered the piping from the
backflow prevention device to the remote control valves. It is generally
the largest pipe on the irrigation system.
Manifold – A group of two or more control valves together in one location
and/or valve box.
Manual System – A system where control valves are operated manually.
Master Valve – An automatic or manual valve installed at the supply point
which controls water flow into the system main line piping.
Matched Precipitation (MPR ) – Matched precipitation means that all
sprinkler heads within a watering zone will produce similar precipitation
rates, regardless of the pattern (or arc) they cover. For example, if a
full circle (360 degree) head delivers 4 gpm, then a half circle (180
degree) head of the same type will produce half that amount, or 2
gpm. The full circle head has twice as much area to cover; therefore,
it needs to put out twice the amount of water as the half circle head.
Some manufacturers have matching precipitation rates within the arc
and the radii. Mixing heads with various radii on the same zone is not
recommended; however, if doing so, the sprinkler heads with different
radii should be grouped separately with heads of like radii in order
to maintain uniform distribution of water and consistent head spacing
within that zone.
Microclimate – relates to the surrounding geographical and environmental
influences that affect an individual site and alter the water scheduling.
This can include (but not limited to): asphalt, pavement, shade, slopes,
and/or wind breaks.
Microclimate Factor – Coefficient used to adjust the potential (or
reference) evapotranspiration in relation to the microclimate (such as
hot, cool, shady, or windy characteristics) of a specific site.
MIP – Abbreviation for “Male Iron Pipe”.
Photo courtesy of I
CHAPTER
MIPT – Abbreviation for “Male Iron Pipe Thread”.
Non-Potable Water – Water not suitable for human consumption.
Non-Volatile Memory – An irrigation controller feature that holds the
program in memory during a power outage without the use of a
battery.
Normally Closed Valve – An automatic valve through which no water will
flow unless external influences are applied to cause the valve to open.
Electrical valves are “normally closed” types.
Normally Open Valve – An automatic valve through which water will flow
unless external influences are applied to close the valve. Hydraulic
valves are “normally open” types.
Nozzle Tree – Refers to the interchangeable nozzle assortment, with different
G.P.M. and radii, provided with many rotary heads.
Pitot Tube – A small tube which can be connected to a pressure gauge to
measure the water pressure at the nozzle of a rotary irrigation head.
Plant Available Water (PA W) = Available Water (AW ) x Root Zone (RZ).
Plant Watering Requirement (PWR) – Same as evapotranspiration
after being adjusted for various factors such as plant species, density,
microclimate, or any specific crop or turf coefficients
P.O.C. - Abbreviation for “Point of Connection”. This is the location where a connection
is made (most commonly) on the service line, followed by the installation of
a backflow device. This is where the irrigation system is connected to any
water source. This the starting point of the irrigation system.
Polyethylene Pipe (P.E.) – Flexible plastic pipe which uses insert fittings.
Potable Water – Water suitable for human consumption. It can be used for
irrigation systems as long as an approved backflow prevention device is
used to protect the potable water supply.
Potential Evapotranspiration (PE T) – evapotranspiration rate of
adequately watered cool season turf approximately 4-7 inches in
height. Also referred to as “Reference Evapotranspiration”.
© Irrigation System Solutions
Photography 2008
Precipitation Rate (PR ) – (See Application Rate)
Pressure – The amount of energy available to move water through the
irrigation components. Usually expressed in PSI.
Pressure Compensating – A method of maintaining a constant discharge
pressure regardless of inlet pressure. Pressure compensating heads,
for example, greatly improve the uniformity of the system. As a
rule of thumb, there should not be more than a 10% difference in
pressure from the first head on a zone to the last head. With pressure
compensating heads, all heads will operate with the same pressure.
Pressure Loss - The loss of pressure caused by friction or increase in elevation.
Pressure Rating - A method of controlling the wall thickness of pipe so all
sizes of pipe in a particular “class” have the same pressure rating. See
definition for S.D.R.
Pressure Regulator – A mechanical device that lowers the water pressure on
the downstream side of the unit. These devices can be adjustable or
have a preset fixed pressure.
Pressure Relief Valve – A valve which will open when the inlet pressure
exceeds a pre-set pressure.
Pressure to Design to – A general rule of thumb used in system design equal
to the low static pressure less 10% allowance for fluctuation. “Design
pressure” should not exceed static pressure less a 10% factor. For
example, if your low static pressure is 60 psi, then your design pressure
should not exceed 54 psi. This allows a buffer to your hydraulics. For
example, if the density of housing increases dramatically over the years,
the pressure may drop enough to significantly affect the operation of
an irrigation system.
Pressure Vacuum Breaker – A backflow prevention assembly that
incorporates a spring-loaded check valve and introduces air into the
system to prevent “back siphonage”. It incorporates the use of a springloaded
seat for positive opening to atmosphere. This device must be
installed at least 12” above all downstream piping and the highest
downstream outlet. It can operate under constant pressure, but cannot
prevent back pressure. This device can be used for both pollutants and
contaminates and can be used for health hazard applications only
where there is no threat of backpressure.
© Irrigation System Solutions
TWCOHAP — CTEROMMON Two — LANDS
Program – Watering information that a user enters into the irrigation controller.
The program determines when and how long the system will water.
P.S.I. – Abbreviation for “Pounds-per-Square-Inch”, a unit of measurement for
water pressure.
Pump – A motorized device which uses mechanical energy to create, or boost,
pressure and water supply for an irrigation system.
Pump Circuit – The optional “switch” on some automatic controllers which
energizes a pump (starter) when controller operation begins.
P.V.C. Pipe – Abbreviation for Poly Vinyl Chloride pipe. This is the most
common pipe used in irrigation systems.
Quick Coupler Valve – A constantly pressurized valve set vertically in the
ground to provide supplemental water (usually to a remote area) when
a coupler key is inserted. It may have a vinyl or plated cover.
Radius – The distance from the center of a circle to the outside curve. The radius
is half the distance of the diameter of the circle. In irrigation, head-tohead
spacing (50%), is 50% of the diameter, or equal to the radius.
Reclaimed Water - Domestic or municipal wastewater which has been
treated to a quality suitable for beneficial use, such as landscape
irrigation (also called “Recycled Water”).
Record Drawing – A drawing of an installed irrigation system showing the
location of major components either scaled on the drawing or shown
by dimension not to scale. To find major components in the future, an
accurate record drawing is necessary, whether it is a formal drawing
or just a sketch. The zone valves are the most important components
to locate accurately on a record drawing. These can be located by
accurate coordinates from a permanent object, using a GPS (Global
Positioning System) unit, taking a picture of the zone valve in reference
to some permanent object, or referencing the location by triangulating
the location from its distance from two separate permanent objects
or reference points. Business note: Record drawings should be filed
according to addresses for easy reference in the future. Remember,
people die or move; however, addresses stay the same.
Reduced Pressure Principle Device (RP , RPP or RP Z) – This backflow
prevention device consists of two independently acting check valves,
together with an automatic operating pressure differential relief valve
located between the two check valves. The first check valve reduces
the supply pressure at a predetermined amount so that during normal
flow, and at cessation of normal flow the pressure between the two
check valves shall be lower than the supply pressure. If either check
valve leaks, the relief valve will discharge to atmosphere. This will
maintain the pressure in the zone between the two check valves lower
than the supply pressure. The unit also has two, resilient seated, shut-off
valves (one upstream and one downstream of the checks) and properly
located test cocks for field testing. It must be installed 12” above
grade in a location that cannot be submerged. This unit can be used to
protect against pollutants or contaminants, can stop backsiphonage and
backpressure, and is required for use for health hazard situations such
as a fertilizer injector being present.
Remote Control Valve – The component that regulates (on command from
the controller) the on/off mode of the water from the main line to the
sprinkler heads. Also referred to as an “Electrical Valve, Hydraulic Valve,
Automatic Control Valve, Section Valve, Circuit Valve, or Zone Valve”.
Resistance – In electrical systems, resistance (measured in ohms) to the flow of
current produces a drop in voltage along a length of wiring. Similar to
friction loss in an irrigation system.
Root Zone – The depth from which roots obtain or extract most of their water.
Also called “Root Depth”.
Rotary Heads – Sprinkler heads that use the energy of the water to rotate
the sprinkler, distributing water (in single or multiple streams) over a
large turf or shrub area. Rotary heads are generally used for larger
landscaped areas. The most common types of rotary heads are the
impact (or impulse), gear and ball driven heads.
Run-Off – During a rain or irrigation event, the water that is not absorbed by the
soil or landscape. If water is applied at a rate faster than the infiltration
rate of the soil, a run-off will result.
Saddle – A type of fitting which attaches around the pipe. A hole is drilled
through the pipe to furnish water to the outlet of the saddle which is
usually threaded F. I. P.
Scheduling – The process of calculating and managing the time and amount
of water to apply to a landscape (see Water Schedule)
Scheduling Coefficient (SC) – The measure of uniformity of water
distribution in a specific landscape irrigated area in relation to the
precipitation rate of the area as a whole. Using a catchment test,
the average precipitation rate for all the catchments is divided by
the lowest precipitation rate, establishing the SC for the system. The
closer this number is to 1, the more uniform the system is. The SC is
an indicator of the additional irrigation run time that is needed to
compensate for the dry areas.
Schedule Pipe – A classification system for pipe designating standard wall
thicknesses for all sizes in which the pipe is made. Most common are
schedules 40 and 80. Schedule 40 has a greater pressure rating than
Class PVC pipe in sizes up to 1 _”. Schedule 40 has the same physical
dimensions as that of steel pipe.
S.D.R. – Abbreviation for “standard dimension ratio”. Relates to wall thickness
of Class PVC pipe. S.D.R. 26 equals Class 160; S.D.R. 21 equals Class
200; S.D.R. 13.5 equals Class 315. No wall thickness can be less than
.060 inches.
Section – The group of sprinklers that are controlled by the same valve. Also
referred to as “station, zone, or circuit”.
Sensors – Refers generally to four types of irrigation sensor units that
automatically assist in the management of irrigation scheduling and
water conservation:
1. Freeze Sensor – Instrument that measures outside temperature
and shuts the system off at a preset temperature. This device
also eliminates the liability issues in cold weather where water
can freeze on walks and streets, creating potentially dangerous
conditions.
2. Rain Sensor – Instrument that measures rainfall and shuts the
system off at a pre-set amount of rain.
3. Wind Sensor – Instrument that measures wind speed and shuts
the system off at a pre-set wind speed.
4. Soil Moisture Sensor – Instrument that monitors the moisture
content in the soil to assist in water scheduling.
Service Line – Generally refers to the piping from the city main to the water
meter. The line that supplies water from the water meter to the house is
also referred to as the service line, or sometimes, the supply line.
Shut-Off Valve – The irrigation component that allows for manual shut-off of
water to the entire irrigation system. This is usually a gate or ball valve.
Sleeves – Piping or conduit under hardscapes (driveways, walks, etc.) for the
purpose of running pipe or wiring. Generally sized two sizes larger
than the irrigation piping.
Slip Fitting – A smooth wall male or female fitting which is solvent welded to
PVC pipe or fitting rather than threaded.
Slope – A measure of the rate of change of elevation over a prescribed
distance. Slope may be expressed as a ratio, a grade, or as a percent.
For example, a ratio of 1 foot vertical to 4 feet horizontal is the same
as a grade of 0.25 (1 divided by 4) which is equal to a percent slope
of 25% (.25 x 100). Another way to express slope is “rise/run”. Divide
the rise (elevation increase) by the run (distance) to get the slope. The
rise can be figured by the contour lines. The run can be computed by
using an appropriate scale and measuring the distance between the
two points in question.
Soil (types of) – There are three basic types of soils: Sand, Silt and Clay.
Most soils are a combination of two or more of these types.
Solenoid – An electromagnet which is located on the valve, connected directly
to the controller, and initiates the opening and closing of the valve.
Solvent – A material which causes a partial dissolving of PCV pipe and fittings
so that a chemical fusion occurs between the pipe and fittings.
Solvent Welding – The act of chemically fusing pipe and fittings together using
solvent. Incorrectly called or referred to as “gluing”.
Spacing – The distance between sprinkler heads. The two most common
spacing types are square and triangular.
Species Factor – Coefficient, reflecting plant species, used to adjust the
reference evapotranspiration.
Spray Heads – Sprinkler heads that throw a uniform sheet of water in a fixed
or adjustable pattern.
Sprinkler Head – Mechanical device which, when under pressure, distributes
water to a given area of landscape.
Standard “Designation Codes” For Pressure Rated
Plastic Pipes:
1120 – PVC pipe, Type one, Grade one, 2000 psi hydrostatic
design stress.
1220 – PVC pipe, Type one, Grade two, 2000 psi hydrostatic
design stress.
2110 – PVC pipe, Type two, Grade one, 1000 psi hydrostatic
design stress.
2306 – Polyethylene pipe, Type two, Grade three, 600 psi
hydrostatic design stress.
Static Pressure – The pressure of water when it is not moving.
Measured in PSI.
Static Water – Refers to water that is not moving.
Station – The group of sprinklers that are controlled by the same valve. Also
referred to as “zone, section, or circuit.”
Surge – An energy wave in pipe lines caused by excessive velocity of flow and
sudden opening or closing of valves. See definition for “water hammer”.
Swing Joint – A flexible joint (composed of a series of threaded risers and 3
elbow connections) or pipe connecting a sprinkler head to a pipe. Intended
to prevent damage to the head due to heavy foot traffic, equipment,
etc. Also used to raise or lower sprinklers to final grade. Some irrigation
professionals prefer swing joints for both commercial and residential
installations. Residential installations typically use a flexible poly-type
swing joint.
Threaded Fitting – A fitting which has I.P.S. threads to receive standard
threaded pipe or fitting.
Thrust Block – A specified amount of concrete poured at strategic points
around larger (generally gasket-type PVC) fittings and pipe where the
water changes direction. The purpose is to secure or brace the joints
from slipping apart when encountering potentially damaging forces
from large volumes of water flowing through the pipe.
Trajectory – The angle of the stream of water as it leaves the sprinkler head.
Higher angle heads generally throw further; however, low angle heads
have less pattern distortion in high winds.
Transpiration – The process of plant material giving off water vapor from the
leaves. This is water the plant actually uses to survive.
Tubing (Spaghetti) – Small tubing used in drip or trickle systems to carry
water from emitter(s) to a specific plant.
Uniformity of Application – A general term designating how uniform the
application of water is over an irrigated area.
Valve – An irrigation component used to control the flow of water. Can be
manual or automatic.
CHAPTER Two — Common Landscape Terminology
34
Valve-in-Head – Indicates that the automatic control valve is part of the
sprinkler. Generally used in golf course systems.
Velocity (of Water) – The speed at which water travels through the piping
systems. Measured in FPS. The generally accepted velocity of water in
PVC or Poly pipe is 5 FPS and 9 FPS in Copper.
Water Hammer – A shock wave in the piping system usually created by
excessive flow velocity and a fast closing valve.
Water Main - The city water piping system located in the street right-of-way.
Water Meter – A mechanical device used to measure the flow of water.
Water Pressure – The force of water in the piping system measured in PSI.
Water Schedule – The procedure of establishing and implementing the
time, frequency, and amount of irrigation water application.
Water Window – An allotted time available for watering through an irrigation
system, usually within a 24 hour period. Depending on the type of
property, the water window can vary significantly. For example,
institutional properties such as a city soccer field will have limited time
to complete water events around ongoing activities.
Working Pressure – The pressure left over in an irrigation system when all
the pressure losses are subtracted from the static pressure. Also called
“dynamic pressure”.
Xeriscape – An alternative method of landscaping using a combination of
seven basic landscaping principles that promote water conservation.
Xeriscaping includes seven basic landscaping principles:26
• Proper planning and design
• Soil analysis and improvement
• Low water plant selection and placement
• Alternative uses for turf areas
• Efficient irrigation
• Mulching
• Proper maintenance of the landscape and irrigation
Zone - The group of sprinklers that are controlled by the same valve. Also
referred to as a “section, station, or circuit”.
within the irrigation industry, regardless of state or region. Reference
materials include, but are not limited to, the Irrigation Association,
Webster’s New World Dictionary, Febco, the Turf Irrigation Manual, the
American Water Works Association (AWWA ), Netafim, Toro, Rain Bird,
the Texas ET web site, and the Texas Commission on Environmental Quality
(TCEQ). These definitions and references do not displace an original
definition or reference.
Absorption Rate – The rate (or speed) at which soil will accept water. The
speed at which water can penetrate or infiltrate the soil. Also called
percolation or infiltration rate. As the soil “capacity” is reached, the
absorption rate will decrease. It is affected by soil type, slope, run-off,
etc. Different soil types absorb water at different rates. For example,
sandy soil, which is very coarse, has the fastest absorption rate, while
clay soil has a slower absorption rate and the greatest horizontal
movement of water.
Active Root Zone – The depth of soil in which a plant extracts most of the
water it needs for evapotranspiration.
Actual Head Pressure – The operating pressure measured at the base of
a sprinkler head. Actual head pressure is calculated by deducting all
pressure losses from the static water pressure. Actual head pressure has
to be equal to, or greater than, the minimum head pressure, for a given
sprinkler head, to function correctly.
Actual Head Pressure = static pressure - all pressure losses
Air Gap – An approved air gap is the unobstructed vertical distance through
free atmosphere between the lowest point of a water supply outlet
and the flood level rim of the fixture or assembly into which the outlet
discharges. These vertical, physical separations must be at least twice
the diameter of the water supply outlet, but never less than 1 in. (25
mm).22 A common air gap would be that of a typical household sink in
which there is an air gap between the water in the sink and the faucet
above it.
Air/Vacuum Relief Valve – Small device used on some subsurface drip
irrigation that allows air into the dripperline when the system is not
running which eliminates any vacuum that could result in debris or
contaminants being sucked into the piping system.
CHAPTER TWCOHAP — CTEROMMON Two — LAND
Allowable Depletion (AD ) – The amount of water, in irrigation
management, that is allowed to be depleted from the plant available
water before an irrigation event is scheduled. Also referred to as
Managed Allowable Depletion (MAD ). Generally, 50% depletion is
the rule of thumb.
Alternating Current (AC) – An electric current that reverses it direction
periodically.
Anti-Siphon Device – Any device that introduces air into the system to
prevent “back siphonage”. Refer to the definitions for atmospheric
vacuum breaker or pressure-type vacuum breaker.
Application Rate – Rate at which water is applied by sprinkler heads in a
certain pattern. Usually measured in inches per hour, gallons per hour
or gallons per day. Commonly called “precipitation rate”. There are
three methods in which to evaluate application rates:
1. A densogram (see definition).
2. Precipitation rate formulas. For example, the following formula
for precipitation rate, the total area method, is one of several
precipitation formulas in chapter 5:
96.3 x Total GPM
Total area
3. A water audit. This is the most accurate method to evaluate
precipitation rates. You are actually collecting water (using
catchment devices) and measuring the actual application rate and
uniformity over a given area.
Aquifer – An underground layer of porous rock, sand, etc. containing water,
into which wells can be sunk.24
Arc – The surface area of the landscape to which a sprinkler head will provide
water. Usually described in degrees or part of a full circle (360
degrees) head. The degrees of coverage of
a sprinkler from one side of a pattern to the
other. For example, a 90-degree arc would be a
quarter circle sprinkler, a 180-degree arc would
be a half circle sprinkler, a 360-degree arc
would be a full circle sprinkler, etc.
Architect Scale – Scale expressing foot measurements in parts of an inch.
Example: 1/8” = 1’, 3/16” = 1’, 1/4” = 1’, etc.
As-Built Plan – A corrected or redrawn plan showing the “actual scaled”
location of all major components of the system and other information Landscape Terminology
the property owner might require. An as-built plan is an invaluable tool
for irrigators to locate major components at a later date. See definition
for “record drawing”.
Atmospheric Vacuum Breaker (AVB) – A backflow prevention device that
allows air into the piping system, with the use of a float that moves up and
down, to prevent backsiphonage. No back pressure can exist for proper
operation. It cannot be under constant pressure for more than 12 hours in
any 24-hour period. This device must be installed vertically and a minimum
of 6” higher than all down stream piping and the highest downstream
head or outlet. There cannot be any shut off valves downstream of the
AVB. A separate AVB must be installed on the discharge side of each
control valve, between the valve and all emission devices.
Automatic Control Valve – An electrical or hydraulic remote control valve
in a sprinkler system which is activated by an automatic controller. Also
called a section valve, circuit valve, zone valve, remote control valve,
electrical valve, or hydraulic valve.
Automatic System – An irrigation system which will automatically cycle
(water) according to a preset program.
Available Water – Water (measured in inch of water per inch of soil) that is
actually accessible for the plant to use.
AWWA – Abbreviation for American Water Works Association.
Backflow – An unwanted reversal of the flow of water in a piping system which
can potentially allow non-potable water to pollute or contaminate the
potable water supply. Caused by backpressure or backsiphonage.
Backpressure – Any condition that could create pressure in the discharge
(outlet or downstream) side of the piping system that is greater than
that of the supply (inlet or upstream) side of the system. Examples of
this occurrence would be pressure caused by gravity (due to elevation),
a pump installed on the system or steam and/or air pressure.
Backsiphonage – A form of backflow due to negative or sub-atmospheric
pressure within water system. A break in the city main line or a fire
department utilizing excessive water to fight a nearby fire could both
induce a backsiphonage.
Backflow Prevention Methods – Any approved device which prevents an
undesirable reversal of flow of water by the introduction of air, use of
check valves, or a combination of both principles. Examples include:
1. An Air Gap
2. An Atmospheric Vacuum Breaker (AVB)
3. A Pressure Vacuum Breaker ( PVB)
4. A Double Check Valve Assembly (DCA )— CTEROMMON Two — LANDS C
5. A Reduced Pressure Principle Device (RP)
Ball Driven Heads – Type of rotary sprinkler in which rotation is achieved by
a steel ball which is set into a circular motion by water passing through
the head.
Block (of heads) – A section of sprinklers controlled by one zone valve.
Body (of heads) – The exterior case or shell of the sprinkler.
Booster Pump – A pump which is installed in the water supply line and is
designed to raise the pressure in the irrigation system.
Bubblers – A type of sprinkler head designed to irrigate level and defined
shrub beds. It is mounted on a riser and puts out a very small umbrella-shaped
adjustable flow of water.
Bushing – The pipe fitting used to change an irrigation component to a larger
or smaller size
Capillary Action – The main effect distributing water horizontally through
the soil.
Catchment Devices – Containers that are used to collect measurable water in
order to conduct a water audit.
C-Factor – Rating of the smoothness of the inside of pipe. The higher the
C-Factor, the smoother the inside diameter of the pipe. PVC has a
C-Factor of 150, whereas copper is 140. Generally, the C-Factor
decreases over time indicating the pipe gets rougher, resulting in
increased friction loss.
Check Valve – A valve which permits water to flow in one direction only.
Class Pipe – A method by which PVC pipe is grouped according to the
working pressure. Pressure rated with a wall thickness in direct ratio
to the diameter. All sizes in that class have the same working pressure.
(Class 125, Class 160, Class 200, Class 315).
Contour Line – A line of equal elevation drawn on a plan. For example, a
contour line labeled “250” means that everywhere along that line is
250 feet above mean sea level. Contour lines are usually accurate to
+/- one-half of the contour interval; ie. when a contour interval of onefoot
is indicated on a plan, a particular contour line will be accurate to
+/- 6 inches.
Control Wires – The wires (from the automatic controller) which transmit
signals to the automatic electrical valves to open and close (see
direct burial wire).
Controller – An automatic timing device, which signals the automatic valves
to open or close according to the prescribed program. Because of
current technological advances, controllers have expanded from very
simple mechanical devices to very sophisticated central control units
that operate numerous satellite units in the field. Wireless automatic
systems are emerging and PC irrigation controller interface hardware
and software solutions are becoming the standard for city parks, golf
and commercial sites. ET -based controllers are becoming very popular.
These innovative controllers will schedule water events based on the
evapotranspiration (ET ) rates (see evapotranspiration). This technology
is becoming standard for the average residential sprinkler system.
Controllers are also referred to as “timers or clocks”.
Coupler Key – A bronze tube with a handle which inserts into a quick coupler
valve (and turned one quarter revolution) for supplemental water. May
be fitted with a sprinkler head, hose swivel or faucet. Also called a
“Quick Coupler Key”. See definition for “quick coupler valve”..
Coverage – The pattern of water that a certain sprinkler covers. Various
sprinklers or sprinkler nozzles have varying patterns of coverage: quarter,
half, full, etc. Most manufacturers even have adjustable arc nozzles that
suffice for many odd-shaped areas.
Cross Connection – Any actual or potential connection between a potable water
supply and any source of contamination or pollution.
Cycle – Refers to one complete operation of the controller through a watering
program.
Density Factor – Coefficient used to adjust the potential (or reference)
evapotranspiration to reflect the usage of water in relation to the
density of the planting.
Design Pressure – The sum total of the desired (or minimum) head pressure
added to the total of all pressure losses. A stated pressure indicating
the minimum pressure required for the system to operate properly. The
design pressure has to be equal to or less than the static pressure for
the system to work.
Design Pressure = Minimum Head Pressure + Total of all Pressure Losses
Desired Head Pressure – The manufacturer’s minimum recommended
operating pressure for a specific head. It is usually stated as the
minimum head pressure.
Densogram – Graphic representation of precipitation. Higher rates are
indicated by darker colors. These are used to check the amount of
precipitation and uniformity in a given irrigation area.
CHAPTER TWCOHAP — CTEROMMON Two — LANDS C
Diameter – Size or dimension of piping.
ID – Inside diameter
OD – Outside diameter
Diaphragm – That portion (flexible membrane) of an automatic valve which
regulates the passage of water through the valve.
Digital Multimeter (DMM ) – A meter (with a digital display) that measures
voltage, ohms and amps. Used in irrigation electrical troubleshooting.
Direct Burial Wire – Any wire approved for direct underground burial without
conduit. UL (underwriters laboratories) approved requires a minimum
insulator thickness of 4/64th”.
Direct Current (DC) – An electric current flowing in one direction.25
Distribution Curve (of a Sprinkler Head) – A curve showing the rate of water
application by a sprinkler at various points along the radius in inches
per hour.
Distribution Uniformity (DU) – The uniformity of the distribution of
water over a given irrigated area. The measure of how uniformly
water is made available to the landscape materials over an area.
DU is expressed as a percentage and generally represents the major
component of irrigation efficiency. It is calculated using a catchment
test. Divide the average reading of the driest 25% (lowest onequarter)
of catch cans by the average reading of all the catchments,
and then multiply by 100. Closer to 100% is better. A DU of 100%
would indicate the area (in question) would be receiving the same
amount of water. 75% - 80% is an excellent DU . 65% - 75% is
considered a good DU reading. Generally, rotary heads have a higher
uniformity than spray heads.
Double Check Valve Assembly (D.C.V.A.) – Backflow prevention
assembly, using two shut-off valves and two check valves assembled
and pre-tested at the factory, designed to physically block or prevent
the backflow of water. For non-health hazard conditions and the
protection of a pollutant only. It will protect against backpressure and
backsiphonage.
Drain Valve – An automatic or manual valve used to drain water from a line
after the system is through running to protect irrigation components
against freeze damage.
Drip Irrigation – The slow application (low volume) of water to the specific
root zone area of the plant material using very low pressure. Usually
expressed in GPH (gallons per hour).
Dry Line Shock (Dry Pipe Shock) – The shock which occurs when a valve is
opened and the water travels unrestricted in empty piping. Air in
the piping is quickly voided through heads at higher velocities than
normal. Unlike water, air is compressible, and can damage irrigation
components such as the heads and piping. It is suggested that (after
the initial installation) irrigators turn the system on slowly, allowing the
piping to gradually fill with water, in order to void most of the air and
minimize component damage.
Dual Programming – The feature on many newer automatic controllers
that allows two or more different watering schedules or programs. Also
called “Multiple Programming”.
Dynamic Water – Water that is in motion through the system. Also referred to
as “Working Pressure”.
Dynamic Pressure – The pressure of water when it is in motion. Also referred
to as “Working Pressure”.
Elevation Gain – Pressure gained as water is used downhill from its source. It
is figured at the rate of .433 pounds per square inch (psi) pressure gain
for each foot of elevation lost.
Elevation Lost – Pressure lost as water is used uphill from its source. Pressure
is lost at the rate of .433 psi for each foot of elevation gained.
Elevation gain or lost works similar to a car coasting up and down a hill.
When a car (already in motion) starts coasting uphill without applying
the throttle or brakes, it begins to lose power similar to water traveling
uphill which loses psi. A car coasting downhill will gain momentum,
similar to water traveling downhill in which it gains psi. However, the
gain or loss of psi of water is due to the weight of the water as a result
of its height above a given point.
Emitters – A small mechanical device (used in drip irrigation) to limit water
flow to a drip or slow trickle. Discharge rate is usually expressed in
gallons per hour rather than gallons per minute.
Engineer’s Scale – Scale expressing foot measurements as a given number of
feet per inch. Example 1” = 10’, 20’, 30’, etc.
Evaporation – The natural process of changing water into vapor.
Evapotranspiration (ET) – The combination of water that has evaporated
from the soil and transpired from the plant material. This is the
measurement of total amount of water needed for plants to grow (See
Evaporation and Transpiration).
Field Capacity – This is the amount of water the soil can retain after the soil
has been saturated and allowed sufficient drainage (usually several
days after a rainfall).
FIP – Abbreviation for “Female Iron Pipe”.
Flow – The movement of water in a piping system. This movement of the water
causes friction loss.
Flow Control Valve – A valve that can be adjusted mechanically to restrict
water flow. This can be referring to a main shut-off valve (such as a
gate or ball valve) or an automatic valve (electrical or hydraulic) which
may have a manual flow control.
Flow Restrictions – Physical restrictions in the irrigation system components
that affect the flow of water causing a pressure loss.
Flush Flow – The higher initial momentary flow through a drip or trickle system
required to flush emitters before pressure compensation occurs. In
drip irrigation systems, flush valves are a desirable, if not necessary,
component to keep lines free of debris.
Flush Valves – A necessary component in drip irrigation systems to keep
lines free of debris. Typically buried in a box with subsurface drip
application, a flush valve allows the velocity of water inside the drip line
to increase momentarily when the system is first turned on. This allows
debris to move out of the system through the flush valve.
Foot-Head “Feet of Head” – A measure of pressure equivalent to .433
pounds per square inch (psi) and equal to the weight of one vertical
foot of water on a one-square-inch surface. Example: a 100’ water
tower equals 100 feet of head or 43.3 psi (100 x .433).
FPS – The abbreviation for “feet per second”.
Friction Loss – Pressure loss due to friction as water flows through all
components (ie. meter, backflow device, zone valves, piping, etc.) of a
system. The rougher the inside surface of the pipe or component, the
more friction loss is encountered.
Gate Valve – Manual valve capable of permitting straight-through, fullopening
flow. These valves are typically used after the POC (point
of connection) and before the backflow device as a manual master
shut-off. Uses a wedge-type metal-to-metal gate or disk for restricting
partial flow. This valve is not recommended for frequent use in throttling
flow in an irrigation system due to the excessive wear on the metal-to metal
parts. To do so may cause leakage. A ball valve is another type
of valve that is preferred and serves the same purpose.
Gauge (Wire) – Standards used for wire sizing. The larger the gauge number,
the smaller the wire diameters. Sizing wire is similar to sizing piping.
The farther the distance, the more friction loss in water flow and more
resistance in wiring is encountered; hence, piping and wiring have to be
sized larger to account for these occurrences.
Gear Driven Heads – Type of rotary sprinkler that has a slower, constant
rotation that is achieved by water passing through a series of gears
within the head.
Globe Valve – A valve which uses a rubber or composition plug against the
valve body seat to restrict or stop the flow of water. Can be either
straight-through or angle configuration.
GPH – Abbreviation for “gallons per hour”. Used when working with lowvolume
irrigation systems such as with drip irrigation.
GPM – Abbreviation for “gallons per minute”, a standard measurement of
water flow.
Gray Water – Domestic wastewater, such as bath, sink, and washing machine
expulsion. It does not include toilet water containing human waste.
Hazard (Degree of) – A measure of the degree of risk or harm to the
public’s health; for example, the term is used to categorize an irrigation
system as a “non-health” or a “health hazard”. A pollutant is a
substance that may affect the color or odor of the water, but not create
a health hazard. This would be considered a low, or non-health hazard.
A contaminant is a substance that may cause illness or death if ingested.
If encountered, this would be classified as a health hazard. Any system
rated as a “health hazard” (such is the case if a fertilizer injector is
installed) must utilize a backflow prevention device requiring annual
testing by a licensed Backflow Prevention Assembly Tester.
Head Spacing – The spacing between sprinkler heads.
Head-to-Head Spacing – Spacing of heads that is equal to the published
radius of the head. This is also referred to as 50% spacing because it
is 50% of the diameter of the head.
CHAPTER TWCOHAP — CTEROMMON Two — LAN
Hydraulically Controlled – A system which uses water pressure through
tubing to operate remote control valves.
Hydraulics – The study of fluid while in motion or at rest. The mechanical
properties of water in motion, or at rest, and the calculation of pressure
losses and irrigation system requirements.
Hydrozone – An irrigation area encompassing plant material with similar
watering requirements due to environmental and/or geographic
influences including, but not limited to, soil type, slope, site orientation,
and solar radiation.
Hygroscopic Water – Water that is held tightly by the soil and inaccessible to
the plants.
Impact Head – A type of rotary sprinkler head that utilizes a driver arm
(mounted on the side) to create rotation.
Infiltration Rate – The speed at which the water can infiltrate the soil. Also
referred to as “Absorption Rate or Percolation Rate”.
In-Line Valve – The component that regulates (on command from the
controller) the on/off mode of the water from the main line to the
sprinkler heads. Also referred to as a remote control valve.
Insert Fitting – A fitting which fits inside the pipe or tubing. Usually used on
polyethylene pipe and tubing.
IPS – Abbreviation for “Iron Pipe Size”.
Irrigation Design – A plan showing graphic or dimensional location of the
components of an irrigation system; ie., sprinkler heads, piping, valves,
backflow prevention device, etc.
Irrigation System – The permanent assembly of irrigation components, such as
heads, valves, pipe, etc., to apply managed water to a given landscaped
area and/or for the purpose of dust reduction or erosion control.
Isolation Valve – An isolation valve, generally a gate or ball valve, serves
as a main shut-off device for the complete irrigation system as needed
for servicing or repair. It must be located between the meter and the
backflow device.
Landscape Irrigation – The art and management of applying water to the
landscape in a manner to encourage the growth of plant material and
support water conservation.
Landscape Coefficient – Coefficient used in adjusting the reference
evapotranspiration by species, density, and microclimate factors.
Lateral Piping – Piping between the remote control valve, not subject to
constant main line pressure, and the sprinkler heads.
LANDSCAPE IRRIGATION TERMINOLOG
Loop Main Line – A main line designed to provide water to any valve from
two or more directions. Using a looped main line greatly improves the
hydraulics.
Main Line – That portion of the irrigation piping normally under constant
pressure, located between the water source and remote control valves
or quick coupler valves. The main line is considered the piping from the
backflow prevention device to the remote control valves. It is generally
the largest pipe on the irrigation system.
Manifold – A group of two or more control valves together in one location
and/or valve box.
Manual System – A system where control valves are operated manually.
Master Valve – An automatic or manual valve installed at the supply point
which controls water flow into the system main line piping.
Matched Precipitation (MPR ) – Matched precipitation means that all
sprinkler heads within a watering zone will produce similar precipitation
rates, regardless of the pattern (or arc) they cover. For example, if a
full circle (360 degree) head delivers 4 gpm, then a half circle (180
degree) head of the same type will produce half that amount, or 2
gpm. The full circle head has twice as much area to cover; therefore,
it needs to put out twice the amount of water as the half circle head.
Some manufacturers have matching precipitation rates within the arc
and the radii. Mixing heads with various radii on the same zone is not
recommended; however, if doing so, the sprinkler heads with different
radii should be grouped separately with heads of like radii in order
to maintain uniform distribution of water and consistent head spacing
within that zone.
Microclimate – relates to the surrounding geographical and environmental
influences that affect an individual site and alter the water scheduling.
This can include (but not limited to): asphalt, pavement, shade, slopes,
and/or wind breaks.
Microclimate Factor – Coefficient used to adjust the potential (or
reference) evapotranspiration in relation to the microclimate (such as
hot, cool, shady, or windy characteristics) of a specific site.
MIP – Abbreviation for “Male Iron Pipe”.
Photo courtesy of I
CHAPTER
MIPT – Abbreviation for “Male Iron Pipe Thread”.
Non-Potable Water – Water not suitable for human consumption.
Non-Volatile Memory – An irrigation controller feature that holds the
program in memory during a power outage without the use of a
battery.
Normally Closed Valve – An automatic valve through which no water will
flow unless external influences are applied to cause the valve to open.
Electrical valves are “normally closed” types.
Normally Open Valve – An automatic valve through which water will flow
unless external influences are applied to close the valve. Hydraulic
valves are “normally open” types.
Nozzle Tree – Refers to the interchangeable nozzle assortment, with different
G.P.M. and radii, provided with many rotary heads.
Pitot Tube – A small tube which can be connected to a pressure gauge to
measure the water pressure at the nozzle of a rotary irrigation head.
Plant Available Water (PA W) = Available Water (AW ) x Root Zone (RZ).
Plant Watering Requirement (PWR) – Same as evapotranspiration
after being adjusted for various factors such as plant species, density,
microclimate, or any specific crop or turf coefficients
P.O.C. - Abbreviation for “Point of Connection”. This is the location where a connection
is made (most commonly) on the service line, followed by the installation of
a backflow device. This is where the irrigation system is connected to any
water source. This the starting point of the irrigation system.
Polyethylene Pipe (P.E.) – Flexible plastic pipe which uses insert fittings.
Potable Water – Water suitable for human consumption. It can be used for
irrigation systems as long as an approved backflow prevention device is
used to protect the potable water supply.
Potential Evapotranspiration (PE T) – evapotranspiration rate of
adequately watered cool season turf approximately 4-7 inches in
height. Also referred to as “Reference Evapotranspiration”.
© Irrigation System Solutions
Photography 2008
Precipitation Rate (PR ) – (See Application Rate)
Pressure – The amount of energy available to move water through the
irrigation components. Usually expressed in PSI.
Pressure Compensating – A method of maintaining a constant discharge
pressure regardless of inlet pressure. Pressure compensating heads,
for example, greatly improve the uniformity of the system. As a
rule of thumb, there should not be more than a 10% difference in
pressure from the first head on a zone to the last head. With pressure
compensating heads, all heads will operate with the same pressure.
Pressure Loss - The loss of pressure caused by friction or increase in elevation.
Pressure Rating - A method of controlling the wall thickness of pipe so all
sizes of pipe in a particular “class” have the same pressure rating. See
definition for S.D.R.
Pressure Regulator – A mechanical device that lowers the water pressure on
the downstream side of the unit. These devices can be adjustable or
have a preset fixed pressure.
Pressure Relief Valve – A valve which will open when the inlet pressure
exceeds a pre-set pressure.
Pressure to Design to – A general rule of thumb used in system design equal
to the low static pressure less 10% allowance for fluctuation. “Design
pressure” should not exceed static pressure less a 10% factor. For
example, if your low static pressure is 60 psi, then your design pressure
should not exceed 54 psi. This allows a buffer to your hydraulics. For
example, if the density of housing increases dramatically over the years,
the pressure may drop enough to significantly affect the operation of
an irrigation system.
Pressure Vacuum Breaker – A backflow prevention assembly that
incorporates a spring-loaded check valve and introduces air into the
system to prevent “back siphonage”. It incorporates the use of a springloaded
seat for positive opening to atmosphere. This device must be
installed at least 12” above all downstream piping and the highest
downstream outlet. It can operate under constant pressure, but cannot
prevent back pressure. This device can be used for both pollutants and
contaminates and can be used for health hazard applications only
where there is no threat of backpressure.
© Irrigation System Solutions
TWCOHAP — CTEROMMON Two — LANDS
Program – Watering information that a user enters into the irrigation controller.
The program determines when and how long the system will water.
P.S.I. – Abbreviation for “Pounds-per-Square-Inch”, a unit of measurement for
water pressure.
Pump – A motorized device which uses mechanical energy to create, or boost,
pressure and water supply for an irrigation system.
Pump Circuit – The optional “switch” on some automatic controllers which
energizes a pump (starter) when controller operation begins.
P.V.C. Pipe – Abbreviation for Poly Vinyl Chloride pipe. This is the most
common pipe used in irrigation systems.
Quick Coupler Valve – A constantly pressurized valve set vertically in the
ground to provide supplemental water (usually to a remote area) when
a coupler key is inserted. It may have a vinyl or plated cover.
Radius – The distance from the center of a circle to the outside curve. The radius
is half the distance of the diameter of the circle. In irrigation, head-tohead
spacing (50%), is 50% of the diameter, or equal to the radius.
Reclaimed Water - Domestic or municipal wastewater which has been
treated to a quality suitable for beneficial use, such as landscape
irrigation (also called “Recycled Water”).
Record Drawing – A drawing of an installed irrigation system showing the
location of major components either scaled on the drawing or shown
by dimension not to scale. To find major components in the future, an
accurate record drawing is necessary, whether it is a formal drawing
or just a sketch. The zone valves are the most important components
to locate accurately on a record drawing. These can be located by
accurate coordinates from a permanent object, using a GPS (Global
Positioning System) unit, taking a picture of the zone valve in reference
to some permanent object, or referencing the location by triangulating
the location from its distance from two separate permanent objects
or reference points. Business note: Record drawings should be filed
according to addresses for easy reference in the future. Remember,
people die or move; however, addresses stay the same.
Reduced Pressure Principle Device (RP , RPP or RP Z) – This backflow
prevention device consists of two independently acting check valves,
together with an automatic operating pressure differential relief valve
located between the two check valves. The first check valve reduces
the supply pressure at a predetermined amount so that during normal
flow, and at cessation of normal flow the pressure between the two
check valves shall be lower than the supply pressure. If either check
valve leaks, the relief valve will discharge to atmosphere. This will
maintain the pressure in the zone between the two check valves lower
than the supply pressure. The unit also has two, resilient seated, shut-off
valves (one upstream and one downstream of the checks) and properly
located test cocks for field testing. It must be installed 12” above
grade in a location that cannot be submerged. This unit can be used to
protect against pollutants or contaminants, can stop backsiphonage and
backpressure, and is required for use for health hazard situations such
as a fertilizer injector being present.
Remote Control Valve – The component that regulates (on command from
the controller) the on/off mode of the water from the main line to the
sprinkler heads. Also referred to as an “Electrical Valve, Hydraulic Valve,
Automatic Control Valve, Section Valve, Circuit Valve, or Zone Valve”.
Resistance – In electrical systems, resistance (measured in ohms) to the flow of
current produces a drop in voltage along a length of wiring. Similar to
friction loss in an irrigation system.
Root Zone – The depth from which roots obtain or extract most of their water.
Also called “Root Depth”.
Rotary Heads – Sprinkler heads that use the energy of the water to rotate
the sprinkler, distributing water (in single or multiple streams) over a
large turf or shrub area. Rotary heads are generally used for larger
landscaped areas. The most common types of rotary heads are the
impact (or impulse), gear and ball driven heads.
Run-Off – During a rain or irrigation event, the water that is not absorbed by the
soil or landscape. If water is applied at a rate faster than the infiltration
rate of the soil, a run-off will result.
Saddle – A type of fitting which attaches around the pipe. A hole is drilled
through the pipe to furnish water to the outlet of the saddle which is
usually threaded F. I. P.
Scheduling – The process of calculating and managing the time and amount
of water to apply to a landscape (see Water Schedule)
Scheduling Coefficient (SC) – The measure of uniformity of water
distribution in a specific landscape irrigated area in relation to the
precipitation rate of the area as a whole. Using a catchment test,
the average precipitation rate for all the catchments is divided by
the lowest precipitation rate, establishing the SC for the system. The
closer this number is to 1, the more uniform the system is. The SC is
an indicator of the additional irrigation run time that is needed to
compensate for the dry areas.
Schedule Pipe – A classification system for pipe designating standard wall
thicknesses for all sizes in which the pipe is made. Most common are
schedules 40 and 80. Schedule 40 has a greater pressure rating than
Class PVC pipe in sizes up to 1 _”. Schedule 40 has the same physical
dimensions as that of steel pipe.
S.D.R. – Abbreviation for “standard dimension ratio”. Relates to wall thickness
of Class PVC pipe. S.D.R. 26 equals Class 160; S.D.R. 21 equals Class
200; S.D.R. 13.5 equals Class 315. No wall thickness can be less than
.060 inches.
Section – The group of sprinklers that are controlled by the same valve. Also
referred to as “station, zone, or circuit”.
Sensors – Refers generally to four types of irrigation sensor units that
automatically assist in the management of irrigation scheduling and
water conservation:
1. Freeze Sensor – Instrument that measures outside temperature
and shuts the system off at a preset temperature. This device
also eliminates the liability issues in cold weather where water
can freeze on walks and streets, creating potentially dangerous
conditions.
2. Rain Sensor – Instrument that measures rainfall and shuts the
system off at a pre-set amount of rain.
3. Wind Sensor – Instrument that measures wind speed and shuts
the system off at a pre-set wind speed.
4. Soil Moisture Sensor – Instrument that monitors the moisture
content in the soil to assist in water scheduling.
Service Line – Generally refers to the piping from the city main to the water
meter. The line that supplies water from the water meter to the house is
also referred to as the service line, or sometimes, the supply line.
Shut-Off Valve – The irrigation component that allows for manual shut-off of
water to the entire irrigation system. This is usually a gate or ball valve.
Sleeves – Piping or conduit under hardscapes (driveways, walks, etc.) for the
purpose of running pipe or wiring. Generally sized two sizes larger
than the irrigation piping.
Slip Fitting – A smooth wall male or female fitting which is solvent welded to
PVC pipe or fitting rather than threaded.
Slope – A measure of the rate of change of elevation over a prescribed
distance. Slope may be expressed as a ratio, a grade, or as a percent.
For example, a ratio of 1 foot vertical to 4 feet horizontal is the same
as a grade of 0.25 (1 divided by 4) which is equal to a percent slope
of 25% (.25 x 100). Another way to express slope is “rise/run”. Divide
the rise (elevation increase) by the run (distance) to get the slope. The
rise can be figured by the contour lines. The run can be computed by
using an appropriate scale and measuring the distance between the
two points in question.
Soil (types of) – There are three basic types of soils: Sand, Silt and Clay.
Most soils are a combination of two or more of these types.
Solenoid – An electromagnet which is located on the valve, connected directly
to the controller, and initiates the opening and closing of the valve.
Solvent – A material which causes a partial dissolving of PCV pipe and fittings
so that a chemical fusion occurs between the pipe and fittings.
Solvent Welding – The act of chemically fusing pipe and fittings together using
solvent. Incorrectly called or referred to as “gluing”.
Spacing – The distance between sprinkler heads. The two most common
spacing types are square and triangular.
Species Factor – Coefficient, reflecting plant species, used to adjust the
reference evapotranspiration.
Spray Heads – Sprinkler heads that throw a uniform sheet of water in a fixed
or adjustable pattern.
Sprinkler Head – Mechanical device which, when under pressure, distributes
water to a given area of landscape.
Standard “Designation Codes” For Pressure Rated
Plastic Pipes:
1120 – PVC pipe, Type one, Grade one, 2000 psi hydrostatic
design stress.
1220 – PVC pipe, Type one, Grade two, 2000 psi hydrostatic
design stress.
2110 – PVC pipe, Type two, Grade one, 1000 psi hydrostatic
design stress.
2306 – Polyethylene pipe, Type two, Grade three, 600 psi
hydrostatic design stress.
Static Pressure – The pressure of water when it is not moving.
Measured in PSI.
Static Water – Refers to water that is not moving.
Station – The group of sprinklers that are controlled by the same valve. Also
referred to as “zone, section, or circuit.”
Surge – An energy wave in pipe lines caused by excessive velocity of flow and
sudden opening or closing of valves. See definition for “water hammer”.
Swing Joint – A flexible joint (composed of a series of threaded risers and 3
elbow connections) or pipe connecting a sprinkler head to a pipe. Intended
to prevent damage to the head due to heavy foot traffic, equipment,
etc. Also used to raise or lower sprinklers to final grade. Some irrigation
professionals prefer swing joints for both commercial and residential
installations. Residential installations typically use a flexible poly-type
swing joint.
Threaded Fitting – A fitting which has I.P.S. threads to receive standard
threaded pipe or fitting.
Thrust Block – A specified amount of concrete poured at strategic points
around larger (generally gasket-type PVC) fittings and pipe where the
water changes direction. The purpose is to secure or brace the joints
from slipping apart when encountering potentially damaging forces
from large volumes of water flowing through the pipe.
Trajectory – The angle of the stream of water as it leaves the sprinkler head.
Higher angle heads generally throw further; however, low angle heads
have less pattern distortion in high winds.
Transpiration – The process of plant material giving off water vapor from the
leaves. This is water the plant actually uses to survive.
Tubing (Spaghetti) – Small tubing used in drip or trickle systems to carry
water from emitter(s) to a specific plant.
Uniformity of Application – A general term designating how uniform the
application of water is over an irrigated area.
Valve – An irrigation component used to control the flow of water. Can be
manual or automatic.
CHAPTER Two — Common Landscape Terminology
34
Valve-in-Head – Indicates that the automatic control valve is part of the
sprinkler. Generally used in golf course systems.
Velocity (of Water) – The speed at which water travels through the piping
systems. Measured in FPS. The generally accepted velocity of water in
PVC or Poly pipe is 5 FPS and 9 FPS in Copper.
Water Hammer – A shock wave in the piping system usually created by
excessive flow velocity and a fast closing valve.
Water Main - The city water piping system located in the street right-of-way.
Water Meter – A mechanical device used to measure the flow of water.
Water Pressure – The force of water in the piping system measured in PSI.
Water Schedule – The procedure of establishing and implementing the
time, frequency, and amount of irrigation water application.
Water Window – An allotted time available for watering through an irrigation
system, usually within a 24 hour period. Depending on the type of
property, the water window can vary significantly. For example,
institutional properties such as a city soccer field will have limited time
to complete water events around ongoing activities.
Working Pressure – The pressure left over in an irrigation system when all
the pressure losses are subtracted from the static pressure. Also called
“dynamic pressure”.
Xeriscape – An alternative method of landscaping using a combination of
seven basic landscaping principles that promote water conservation.
Xeriscaping includes seven basic landscaping principles:26
• Proper planning and design
• Soil analysis and improvement
• Low water plant selection and placement
• Alternative uses for turf areas
• Efficient irrigation
• Mulching
• Proper maintenance of the landscape and irrigation
Zone - The group of sprinklers that are controlled by the same valve. Also
referred to as a “section, station, or circuit”.