Chapter 2 - Common Terminology and System Components - Irrigation Basics

Pressure Vacuum Breaker

A backflow prevention assembly that introduces air into the system to prevent "back siphonage". Incorporates the use of a spring-loaded seat for positive-opening to the atmosphere. This assembly can be under constant pressure. Commonly used for high hazard application where there is no backpressure. The assembly must be installed at least 12" above all downstream piping and the highest downstream outlet.

Atmospheric Vacuum Breaker (AVB)

A backflow prevention device, which introduces air into the piping system to prevent back siphonage. This device cannot be under constant pressure (more than 12 hours). It must be installed at least 6" higher than all downstream piping and the highest downstream outlet. No back-pressure may exist. No shut-off valves may exist downstream of the AVB.

Quick Coupler Key

A bronze tube with a handle which inserts into a quick coupling valve for supplemental water. May be fitted with a hose swivel.

Schedule Pipe

A classification system for pipe. It is PVC pipe that has the same physical dimensions as iron-pipe.

Quick Coupling Valve

A constantly pressurized valve set vertically in the ground to provide supplemental water when a coupler key is inserted.

As Built Plan

A corrected or redrawn plan (to scale) showing the actual location of all major components of the system and other information the property owner might require.

Record Drawing

A drawing of an installed irrigation system showing the location of major components either scaled on the drawing or shown by dimensions not to scale.

Insert Fittings

A fitting that fits into pipe or tubing. Usually used on polyethylene pipe and tubing.

Threaded Fitting

A fitting that has I.P.S. threads to receive a standard pipe thread or fitting.

Seing Joint

A flexible joint connecting a sprinkler head to a pipe. The swing joint is intended to provide protection from damage.

Back Siphonage

A form of backflow due to negative or sub-atmospheric pressure within a potable water system.

Section of Heads

A group of sprinklers controlled by one valve. Also known as a "zone."

Contour Line

A line of equal elevation drawn on a plan. For example, a contour line labeled "510" means that everywhere along that line is approximately 510 feet abo e mean sea level. Contour lines are usually accurate to plus or minus one-half of the contour interval. That is, when a contour interval of one-foot is indicated on a plan, a particular contour line will be accurate to plus or minus 6 inches.

Loop Main Line

A main line designed to provide water to any valve from two or more directions.

Solvent

A material that causes a partial dissolving of PVC pipe and fittings so a chemical fusion occurs between the pipe and fitting.

Feet of Head (Foot-Head)

A measure of pressure equivalent to .433 psi and equal to the weight of 1 foot of water on a one square inch surface.

Hazard (Degree Of)

A measure of the degree of risk or harm to the public's health; for example, the term used to categorize an irrigation system as "low hazard" or a "high-health hazard".

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 grade of 0.25, which is equal to a percent slope of 25%. Slope = Rise/Run.

Emitters

A mechanical device used in drip irrigation to limit water flow to a drip or slow trickle. Discharge rate in gallons per hour rather than gallons per minute.

Class Pipe

A method by which PVC pipe is grouped according to the working pressure. Class 160, Class 200, Class 315 are examples of classes of pipe (class 200 pipe can be used where pressures do not exceed 200 psi)

Pressure Rating

A method of controlling the wall thickness of PVC pipe so all sizes of pipe in a "class" has the same pressure rating. See definition for S.D.R.

Pressure Compensating

A method of maintaining a constant discharge pressure regardless of inlet pressure.

Bushing

A pipe fitting used to change to either a larger or smaller size.

Design

A plan showing graphic or dimensional location of component parts of an irrigation system, such as sprinkler heads, piping, valves, backflow prevention device, etc.

Booster Pump

A pump that is installed on the water supply line and is designed to raise the operating pressure in the irrigation system.

Water Hammer

A shock wave in the piping system usually created by an excessive flow velocity and a fast closing valve. Increase back pressure of the shock wave could result in unwanted backflow.

Slip Fitting

A smooth wale male or female fitting solvent welded to PVC pipe or fitting rather than threaded.

Hydraulically Controlled

A system using water pressure through tubing to operate remote control valves.

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.

Flow Control Valve

A valve that can be mechanically adjusted to restrict water flow.

Check valve

A valve that permits water to flow in one direction only.

Globe Valve

A valve that uses a rubber or composition plug against a valve body seat to restrict or stop the flow of water. Can be either straight through or angle-configuration. A globe valve is recommended for use as a section valve for an irrigation system.

Pressure Relief Valve

A valve that will open when the inlet pressure exceeds a pre-set pressure.

FIP

Abbreviation for "Female Iron Pipe".

G.P.H.

Abbreviation for "Gallons per Hour".

G.P.M.

Abbreviation for "Gallons per Minute".

IPS

Abbreviation for "Iron Pipe Size".

MIP

Abbreviation for "Male Iron Pipe".

P.O.C.

Abbreviation for "Point-of-Connection".

P.V.C. Pipe

Abbreviation for "PolyVinyl Chloride" Pipe.

PE

Abbreviation for "Polyethylene"

P.S.I.

Abbreviation for "Pounds-per-Square-Inch".

S.D.R.

Abbreviation for "standard dimension ratio". Relates to wall-thickness of Class 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.

AWWA

Abbreviation for American Water Works Association. Mainly used for cast iron and asbestos-cement pipe. Devises industry material manufacturing, handling, and installation standards.

Matched Precipitation

All heads discharge varying amounts of water, combining to produce uniform coverage. Ex: if a full circle head discharges at 4 gpm, a half circle head will discharge 2 gpm.

Precipitation Rate

Also known as application rate. The rate at which water is applied by the irrigation system. It is usually measured in inches per hour or gallons per hour. Often referred to as precipitation rate. The following formula is used to figure precipitation rate: GPM (full circle of head) * 96.3 / Head Spacing * Row Spacing -or- Total GPM * 96.3 / Total Area

Application Rate

Also known as precipitation rate. The rate at which water is applied by the irrigation system. It is usually measured in inches per hour or gallons per hour. Often referred to as precipitation rate. The following formula is used to figure precipitation rate: GPM (full circle head) * 96.3 ------------------------------- Head Spacing * Row Spacing -- or -- Total GPM * 96.3 ------------------- Total Area

ANSI

American National Standards Institute. The official representative of the United States in the field of standards.

ASSE

American Society of Sanitary Engineers. Devises industry material manufacturing, handling, and installation standards.

ASTM

American Society of Testing and Materials. Set standards for thermoplastic pipe and copper water tube.

Cross-connection

An actual or potential connection between a potable water supply and any source of contamination or pollution.

Water Window

An allotted time available to water through an irrigation system, usually within a 24-hour period.

Master Valve

An automatic or manual valve installed at the supply point, which controls water flow into the system main-line piping.

Drain Valve

An automatic or manual valve used to drain water from a line after the system has operated.

Controller

An automatic timing device, which may be electro-mechanical, digital or a combination of both, and signals the automatic valves to open or close according to a prescribed program.

Normally Closed Valve

An automatic valve through which no water will flow unless external influences are applied to open the valve. Most electric valves are "normally closed" type.

Normally Open Valves

An automatic valve through which water will flow unless external influences are applied to close the valve. Almost all hydraulic valves are "normally open" type.

Automatic Control Valve

An electric or hydraulic remote control valve in a sprinkler system that is activated by an automatic controller. Also called a section valve, zone valve, or remote control valve.

Surge

An energy wave in pipe-lines caused by an excessive velocity of flow and sudden opening and closing of valves. See "Water Hammer"

Manual System

An irrigation system where control valves are operated manually.

Automatic System

An irrigation system which will automatically cycle according to a preset program.

Backflow

An undesired reversal of the flow of water in a piping system. Caused by back pressure or back siphonage.

Backflow Prevention Device

Any approved method that prevents an undesirable reversal of flow of water.

Back Pressure

Any condition that could create pressure in the discharge (outlet or downstream) side of the piping system that is greater than in the supply (inlet or upstream) side of the system. Examples: Pressure cause by gravity due to elevation differences; a pump installed in the system; or steam and/or air pressure.

Anti-siphone Device

Any device that introduces air into the system to prevent "back siphonage". See definitions for atmospheric vacuum breaker or pressure-type vacuum breaker below.

Direct Burial Wire

Any wire approved for the direct underground burial without conduit.

Double Check Valve Assembly (D.C.V.A.)

Backflow prevention assembly using two shut-off valves and two check valves assembled and pretested at the factory, designed to physically prevent the backflow of water. May be used only in low hazard conditions.

Polyethylene pipe (P.E. Pipe)

Flexible plastic pipe

Valve-In-Head

Indicates that the automatic control valve is part of the sprinkler.

Gate Valve

Manual valve capable of permitting straight-through, full open flow. The valve uses a wedge type metal-to-metal gate or disk for restricting partial flow. The gate valve is not recommended for use to throttle flow in an irrigation system. The gate valve is not recommended for use as a section valve for an irrigation system.

NSF

National Sanitation Foundation

Actual Head Pressure

Operating pressure at the base of the sprinkler head. Calculated by subtracting all pressure losses, between the head and the pressure source, from the static pressure at the source.

Flow Restrictions

Physical restrictions in component parts of an irrigation system that affect the flow of water thus causing a pressure loss.

Lateral Piping

Piping after the remote control valve not subject to constant main line pressure.

Sleeves

Piping or conduit under hardscape provided for irrigation system piping or wiring. Generally sized 2 sizes larger than irrigation piping required. If in a high traffic area it is recommended the sleeve be at least schedule 40 PVC.

Elevation Gain

Pressure gained as water is used downhill from its source. It is figured the pressure gain rate of .433 pounds per square inch for each foot of elevation lost.

Friction Loss

Pressure loss due to friction as water flows through the component parts of a system.

Elevation Loss

Pressure lost as water is used uphill from its source. It is lost at the rate of .433 psi for each foot of elevation gained.

R.P.Z. or R.P.

Reduced pressure zone backflow prevention assembly commonly used for high hazard applications. Uses a combination of check valves and an air chamber or zone, which will open to atmosphere when failure occurs. Must be used if chemicals are added to the system.

Cycle

Refers to one complete operation of a controller through a watering program.

Nozzle Tree

Refers to the interchangeable nozzle assortment, with different GPM and radiuses, provided with many rotor heads.

Head to Head Spacing

Spacing of heads that is equal to the published radius.

Triangular Head Spacing

Spacing where heads of each row are offset so that the heads form an equilateral triangle. The following formula is used to determine triangular row spacing: Row Spacing = Head Spacings * 0.866 Triangular Head Spacing is most recommended by manufacturers of rotary heads.

Gauge (Wire)

Standards used for wire sizing. the larger the gauge number, the smaller the wire.

Diaphragm

That portion (flexible membrane) of an automatic valve that regulates the passage of water through the valve.

Main Line

That portion of the piping, normally under constant pressure, located between the water source and remote control valves or quick coupler valves.

Solvent Welding

The act of chemically fusing pipe and fittings together using solvent. Incorrectly called or referred to as gluing.

Evapotranspiration

The combination of evaporation and transpiration through plant material.

Design Pressure

The desired head pressure added to all pressure losses that occur when supplying water to a specific head. A stated pressure indicating the minimum pressure required if the system is to operate properly.

Multiple Programming

The feature on some automatic controllers that allows more than one watering schedule or program.

Flush Flow

The higher initial momentary flow through a drip or trickle system required to flush emitters before pressure compensation occurs.

Pressure Loss

The loss of pressure under flow conditions caused by friction or elevation.

Desired Head Pressure

The manufacturer's minimum recommended operating pressure for a specific head.

Distribution Uniformity (DU)

The measure of the uniformity of irrigation water over an area. The measure of how uniformly water is made available to the plants over an area. DU is expressed as a percentage and generally represents the major component of irrigation efficiency. A DU of 1.0 (100% uniformity) represents all of that area will receive the same amount of water.

Static Pressure

The measured pressure of water when it is not moving.

Flow

The movement of water in a piping system.

Evaporation

The natural process of changing water into vapor.

Pump Circuit

The optional "switch" on some automatic controllers, which energizes a pump (starter) when controller operation begins.

Dynamic Pressure

The pressure of water as it is moving through the system. Also referred to as "Working Pressure".

Water Schedule

The procedure of establishing and implementing the time, frequency, and amount of irrigation water application.

Transpiration

The process of plant material giving off water vapor from the leaves.

Absorption Rate

The rate at which soil will accept water. Rate decreases as soil "capacity" is reached. Affected by soil type, slope, run-off, etc. (Also called percolation rate, infiltration rate).

Dry Line Shock (Dry Pipe Shock)

The shock occurring when a section valve is opened and the water travels unrestricted in empty lateral piping. Air in the piping is quickly voided through heads allowing velocities that would not normally occur. Damages heads, piping or other component parts.

Drip Irrigation

The slow application (low volume) of water, usually under low pressure, to the specific root zone area of the plant material.

Head Spacing

The spacing between sprinkler heads.

Velocity (of water)

The speed at which water travels through piping.

Arc

The surface area of the landscape to which the head will provide water. Usually described in degrees or part of a circle. For example, a 90-degree arc would be a quarter circle sprinkler.

Control Wires

The wire that transmits the signals from the automatic controller to the automatic electric valves to open and close the valves.

Soil, Type of

There are three basic types of soils: Sand, Silt, and Clay. Most soils are a combination of these types. Water moves horizontally through soil by means of "Capillary action". Water moves downward through soil by means of capillary action AND gravity.

Non-Potable Water

Water not suitable for human consumption.

Potable Water

Water suitable for human consumption. May be used for irrigation systems as long as approved backflow prevention is used to protect the water supply.

Which has the highest pressure loss? a. 1" globe valve b. 1" gate valve c. 1" ball valve d. the pressure loss is the same in all of the above

a. 1" globe valve

AWWA is the abbreviation for _____. a. American Water Works Association b. American Waste Water Association c. Association of Waste Water Activites d. None of These

a. American Water Works Association

Erratic rotation of rotary heads will adversely affect ________. a. Uniform precipitation b. head setting c. discharge rate d. head pressure

a. Uniform precipitation

Type of valve recommended to be used as section valves. a. globe valve b. gate valve c. ball valve d. check valve

a. globe valve

Absorption rate is also known as ____. a. infiltration rate b. precipitation rate c. field capacity d. application rate

a. infiltration rate

What can be used to empty the water in your lateral lines? a. flush valve b. drain valve c. electric valve d. master valve

b. drain valve

Which is not a type of rotary head? a. impact b. pin drive c. ball driven d. gear driven

b. pin drive

Backflow prevention devices prevent the backflow of water by: a. introduction of air b. use of check valves c. both a & b d. none of these

c. both a & b

Type of spray head found in flowerbeds. a. turf spray head b. surface spray head c. shrub spray head d. rotary head

c. shrub spray head

Direct burial wire used for irrigation should be ________. a. no smaller than 16 gauge b. no larger than 12 gauge c. multi-conductor d. UL listed

d. UL listed

The minimum pressure needed for your system to operate properly. a. actual head pressure b. head pressure c. static pressure d. design pressure

d. design pressure

Flexible membrane inside an electric valve that allows water to pass through. a. bonnet b. solenoid c. bleed screw d. diaphragm

d. diaphragm