Absorption Rate

The rate at which a soil will accept water. Rate decreases as soil “capacity” is reached and is affected by soil type, slope, run-off, etc. It is also referred to as “percolation rate” or “infiltration rate”.

Actual Head Pressure (Dynamic 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. It is also referred to as “dynamic head pressure” or “working head pressure”.

Air Gap

A complete physical separation between the free flowing discharge end of a potable water supply pipeline and an open or non-pressure receiving vessel.

Anti-siphon Device

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

Application Rate (Precipitation Rate)

The rate at which water is applied by the irrigation system. It is usually measured in inches per hour. Often referred to as precipitation rate. The following formulas are used to calculate precipitation rate:

GPM (full circle head) x 96.3

Head Spacing x Row Spacing

or

Total GPM x 96.3

Total Area

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.

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.

Atmospheric Vacuum Breaker (AVB)

An assembly containing an air inlet valve, a check seat and an air inlet port. The flow of water into the body causes the air inlet valve to close the air inlet port. When the flow of water stops the air inlet valves falls and forms a check against back siphonage. At the same time it opens the air inlet port allowing air to enter and satisfy the vacuum. 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 be installed down-stream of the AVB.

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.

Automatic System

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

Back Pressure

Any pressure, regardless of its source, against the outlet side of the backflow prevention device, which exceeds the supply pressure against the inlet side of the device. Examples: Pressure caused by gravity due to elevation differences; a pump installed in the system; or steam and/or air pressure.

Back Siphonage

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

Backflow

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

Backflow Prevention

The mechanical prevention of reverse flow, or back siphonage, of non-potable water from an irrigation system into the potable water source.

Backflow Prevention Assembly

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

Bushing

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

Check Valve

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

Class Pipe

The Texas Commission on Environmental Quality.

Consulting

The act of providing advice, guidance, review or recommendations related to landscape irrigation systems.

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 above 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.

Control Wires

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

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.

Council

The Texas Irrigator Advisory Council.

Cross-connection

An actual or potential connection between a potable water source and an irrigation system that may contain contaminates or pollutants, or any source of water that has been treated to a lesser degree in the treatment process.

Cycle

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

Design

The act of determining the various elements of a landscape irrigation system that will include, but is not limited to, elements such as collecting site specific information, defining the scope of the project, defining plant watering needs, selecting and laying out emission devices, location system components, conducting hydraulic calculations, identifying any local regulatory requirements or scheduling irrigation work at a site. Completion of the various components will result in an irrigation plan.

Design Pressure

The pressure that is required for an emission device to operate properly. Design pressure is calculated by adding the operating pressure necessary at an emission device to the total of all pressure losses accumulated from an emission device to the water source.

Direct Burial Wire

Any wire approved for direct underground burial without conduit.

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 that all of the area will receive the same amount of water.

Diaphragm

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

Double Check Valve Assembly (DCVA)

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 that all of the area will receive the same amount of water.

Diaphragm

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

Double Check Valve Assembly (DCVA)

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

Drain Valve

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

Drip Irrigation

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

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 piping is quickly voided through heads allowing velocities that would not normally occur. Dry line shock can damage heads, piping or other component parts.

Dynamic Pressure

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

Emission Device

Any device that is contained within an irrigation system that is used to apply water. Common emission devices in an irrigation system include spray and rotary sprinkler heads, and drip irrigation emitters.

Emitters

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

Evaporation

The natural process of changing water into vapor.

Evapotranspiration (ET)

The combination of evaporation and transpiration through plant material. It is often used as a measurement of the amount of water that should be replaced when irrigating plant material.

Flow

The movement of water in a piping system. Often expressed in gallons per minute or cubic feet per second.

Flow Control Valve

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

Flow Restrictions

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

Feet of Head (Foot-Head)

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

Friction Loss

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

Gate Valve

Manual valve capable of permitting full open flow resulting in very low friction loss. 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.

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.

Gauge (Wire)

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

Head Spacing

The spacing between sprinkler heads.

Head to Head Spacing

Spacing of heads that is equal to the published radius.

Health Hazard

A cross-connection or potential cross-connection with an irrigation systems that involves any substance that may, if introduced into the potable water supply, cause death or illness, spread disease, or have a high probability of causing such effects.

Hydraulics

The science of dynamic and static water; the mathematical computation of determining pressure losses and pressure requirements of an irrigation system.

Hydraulically Controlled

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

Insert Fittings

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

Irrigation Inspector

A licensed plumbing inspector, water district operator, other governmental entity, or irrigation inspector who inspects irrigation systems and performs other enforcement duties for a municipality or water district as an employee or as a contractor. A city can only use a licensed irrigation inspector or plumbing inspector, whereas, a water district can use all four entities for inspections.

Irrigation Plan

A scaled drawing of a landscape irrigation system which lists required information, scope of the project and represents the changes made in the installation of the irrigation system.

Irrigation System

An assembly of component parts permanently installed for the controlled distribution and conservation of water for the purpose of irrigating any type of landscape vegetation or in an effort to reduce dust or control erosion. This includes parts used in the application and installation of drip irrigation systems. The term does not include a system used on or by an agricultural operation as defined by Texas Agricultural Code, 251.002.

Irrigation Technician

A person who works under the supervision of a licensed irrigator to install, maintain, alter, repair, service or supervise installation of an irrigation system, including the connection of the irrigation system to a private or public, raw or potable, water supply system or any water supply, and who is required to be licensed.

Irrigation Zone

A subdivision of an irrigation system with a matched precipitation rate based on plant material type, microclimate factors, topographical features and soil conditions or for hydrological control.

Irrigator

A person who sells, designs, offers consulting regarding installs, maintains, alters, repairs, services or supervises the installation of an irrigation system, including the connection of the irrigation system to a private or public, raw or potable water supply system or any water supply, and who is required to be licensed.

Irrigator-in-Charge

The irrigator responsible for all irrigation work performed by an exempt business owner, including permits, design plans, supervision of other licensed irrigators/technicians, as well as installing, selling, maintaining, altering, repairing or servicing a landscape irrigation system. An individual may work for other entities, but can only be designated as the Irrigator-in-Charge at one entity.

Landscape Irrigation

The science of applying water to promote and/or sustain growth of plant material or turf.

Lateral Piping

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

Loop Mainline

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

Mainline

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

Maintenance Checklist

A document made available to the irrigation system’s owner or owner’s representative that contains information regarding the operation and maintenance of the irrigation system, including, but not limited to: checking and repairing the irrigation system, setting the automatic controller, checking the rain or moisture sensor, cleaning filters, pruning grass and plants away from irrigation emitters, using and operating the irrigation system, the precipitation rates of each irrigation zone within the system, any water conservation measures currently in effect from the water purveyor, the name of the water purveyor, a suggested seasonal or monthly watering schedule based on current evapotranspiration data for the geographic region, and the minimum water requirements for the plant material in each zone based on the soil type and plant material where the system is installed.

Manual System

An irrigation 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. If a master valve is installed, it must be installed after the backflow prevention device.

Matched Precipitation

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

Multiple Programming

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

Non-Health Hazard

A cross-connection or potential cross-connection from a landscape irrigation system that involves any substance that generally would not be a health hazard but would constitute a nuisance or be aesthetically objectionable if introduced into the potable water supply.

Non-Potable Water

Water not suitable for human consumption.

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 Valve

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.

Nozzle Tree

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

Pass-Through Contract

A written contract between a contractor or builder and a licensed irrigator or exempt business owner to perform part or all of the irrigation services related to an irrigation system. 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.

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.

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. The following formula is used to figure precipitation rate:

GPM (full circle head) x 96.3

Head Spacing x Row Spacing

or

Total GPM x 96.3

Total Area

Pressure Compensating

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

Pressure Loss

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

Pressure Rating

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

Pressure Relief Valve

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

Pressure Vacuum Breaker (PVB)

An assembly containing an independently operating, internally loaded check valve and an independently operating, loaded air inlet valve located on the discharge side of the check valve. Commonly used for high hazard application where there is no back pressure. The assembly must be installed at least 12” above all downstream piping and the highest downstream outlet.

Pump Circuit

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

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.

Quick Coupling Valve

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

Reclaimed Water

Domestic or municipal wastewater which has been treated to a quality suitable for beneficial use, such as landscape irrigation.

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.

Reduced Pressure Principle Backflow Prevention Assembly (RPBA, RP, RPZ)

An assembly containing two independently acting, approved check valves together with a hydraulically operating, mechanically independent, pressure differential relief valve located between the two check valves and below the first check valve. Must be used if chemicals are to be added to the system.

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.

Schedule Pipe

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

Section of Heads

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

Sleeves

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

Slip Fitting

A smooth wall male or female fitting 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 grade of 0.25, which is equal to a percent slope of 25%.

Slope = Rise ÷ Run

Soil, Types 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.

Solvent

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

Solvent Welding

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

Static Pressure

The measured pressure of water when it is not moving.

Surge

An energy wave in pipe lines caused by excessive velocity of flow and sudden opening and closing of valves. See “water hammer”.

Swing Joint

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

Threaded Fitting

A fitting that has IPS threads to receive a standard pipe thread or fitting.

Transpiration

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

Triangular Head Spacing

Spacing where the 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 Spacing X 0.866

Valve-In-Head

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

Velocity (of water)

The speed at which water travels through piping.

Water Hammer

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

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.