Glossary

Speak The Language – Irrigation Terms You Will Need to Know

ANTI-SIPHON DEVICE
A type of backflow preventer which seals off the atmospheric vent area when the system is pressurized. Should be installed downstream of a control valve in a location which is at least twelve inches higher than the highest point in the lateral which it serves. When system pressure drops to zero, the float and seal assembly drops, opening the vent to atmosphere and breaking any siphon effect. Consult local building codes or your Rain Bird distributor for laws applicable in your area. Synonymous with Atmospheric Vacuum Breaker.

ANTI-SIPHON VALVE
The combination of an angle valve and anti-siphon device in one unit. The anti-siphon device is located downstream of the angle valve.

APPLICATION RATE
A measurement of the volume of water applied to landscape in a given time. (In the United States, usually expressed in inches per week. Its metric equivalent is centimeters per week.)

ARC
The area a part-circle sprinkler irrigates, expressed in degrees of a circle. For example, a 90 degree arc provides quarter-circle coverage, while an 180 degree arc provides half-circle coverage.

AUTOMATIC CONTROL VALVE
A valve which is activated by an automatic controller using electric or hydraulic means. Synonymous with Remote Control Valve.

BACKFLOW
The unwanted reverse flow of liquids in a piping system.

BACKFLOW PREVENTER
A mechanical device which prevents backflow. In irrigation, it is used to protect the potable water supply from potentially contaminated irrigation water. There are several types of backflow preventers. The choice of backflow preventer used depends on the degree of hazard and the particular piping arrangement involved. Virtually all regulatory agencies in the United States require backflow prevention devices to protect the domestic water supply from contamination by the backflow of irrigation water. In areas where it is not required, it is highly recommended. Consult local building codes for laws applicable in your area.

CHECK VALVE
A valve which allows water to flow in one direction only. Check valves are used to prevent low head drainage.

CONTROLLER or TIMER or CLOCK
This is the brain of the sprinkler system. The controller automatically opens and closes valves according to a preset schedule. Rain Bird controllers have easy-to-set programs to help you efficiently manage seasonal adjustments. Rain Bird also has sensors that signal the controller to shut off the system when it rains. An automatic controller is usually more water-efficient that operating sprinklers manually.

COVERAGE
The area of landscape watered by a sprinkler or grouping of sprinklers.

DIAPHRAGM
Rubberized seal which keeps water from flowing through the valve.

DIAPHRAGM VALVE
A globe or angle pattern valve which uses a diaphragm to control the flow of water through the valve.

DRAIN VALVE
A valve used to empty water from a lateral or main line, usually for winterization purposes.

DRIP IRRIGATION
A low volume watering method that delivers water slowly and directly to the plant roots for maximum efficiency.

EMITTER
A small watering device which delivers water at very low rate (measured in gallons per hour) and pressure at the outlet port.

EXTERNAL MANUAL BLEED
A feature which allows an automatic valve to be opened manually (without controller) by releasing water from above the diaphragm to the outside of the valve. Useful during installation, system start-up and maintenance operations.

FLOW
The movement of water.

FLOW CONTROL
A valve which modulates in order to maintain a pre-determined flow rate without drastically altering the pressure.

FLOW SENSOR
A device which actively measures water flow through a piping system and reports its data to the computerized central control system.

GLOBE VALVE
A valve configured with its outlet oriented 180 degrees from its inlet. In irrigation, these valves are generally installed so that the inlet and outlet are parallel to the ground.

GPM
Acronym for gallons per minute.

HEAD TO HEAD COVERAGE
The practice of placing sprinklers so that water from one sprinkler overlaps all the way to the next sprinkler head.  This helps to increase overall system efficiency and prevents dry spots in the landscape.

IMPACT DRIVE
A sprinkler which rotates using a weighted or spring-loaded arm which is propelled by the water stream and hits the sprinkler body, causing movement around a circle.

INFILTRATION RATE
The rate at which water enters the soil, usually expressed in depth of water per hour. (In the United States, usually expressed in inches per hour. Its metric equivalent is centimeters per hour.)  Infiltration rate is determined by the type of soil.

IRRIGATION SYSTEM
A set of components which includes the water source (e.g., domestic service or pump), water distribution network (e.g., pipe), control components (e.g., valves and controllers), emission devices (e.g., sprinklers and emitters) and possibly other general irrigation equipment (e.g. quick coupler and backflow preventer).

IRRIGATION REQUIREMENT
The quantity of water needed by the landscape to satisfy the evaporation, transpiration and other uses of water in the soil. The Irrigation requirement is usually expressed in depth of water and equals the net irrigation requirement divided by the irrigation efficiency. (In the United States, usually expressed in inches per week. Its metric equivalent is centimeters per week.)

MAIN (MAINLINE)
A pipe under constant pressure which supplies water from the point of connection to the control valves.

MASTER VALVE
A valve used to protect the landscape from flooding in case of a ruptured main or malfunctioning downstream valve. The master valve is installed on the mainline after the backflow preventer and the control valves.

MATCHED PRECIPITATION RATE (MPR)
Matched precipitation rate (MPR) refers to sprinklers that apply water at the same rate per hour no matter the arc of coverage or part of a circle they cover. For instance, a full-circle sprinkler discharges twice the flow of a half-circle sprinkler and a quarter-circle sprinkler discharges half of what the half-circle unit does. MPR allows the same type of sprinklers, no matter what their arc, to be circuited on the same valve and to deliver the same PR rate. Spray heads have fixed arcs and are matched by the manufacturer, while rotors offer a choice of nozzles to match the Designed arc pattern.

MOISTURE SENSOR
A device which monitors the amount of water present in the soil and modifies the watering schedule accordingly.

NOZZLE
The final orifice through which water passes from the sprinkler or emitter.  Nozzle shape, size and placement has a direct effect on the distance, watering pattern and distribution efficiency.

OPERATING PRESSURE
The pressure at which a system of sprinklers operates. Static pressure less pressure losses. Usually as measured at the base or nozzle of a sprinkler.

PRECIPITATION RATE (PR)
The rate at which a sprinkler system applies water to the landscape. PR is expressed in depth of water per hours of operation. (In the United States, usually expressed in inches per hour. Its metric equivalent is centimeters per hour.)

PRESSURE
The force per unit area measured. (In the United States, usually expressed in pounds per square inch. Its metric equivalent is Bars.)  Insufficient water pressure can result in poor sprinkler coverage, while excessively high water pressure may cause misting and fogging leading to water waste.

PRESSURE REGULATOR
A device which maintains constant downstream operating pressure which is lower than the upstream operating pressure.

PROGRAM
The watering plan or schedule that tells the controller exactly when and how long to run each set of sprinklers. Many Rain Bird controllers offer multiple programs which can be useful on sites where different plant groups have different irrigation needs.

PSI
Acronym for pounds per square inch.

PUMP START RELAY
Low-amperage or electric switch designed for use with pump start circuits.

RAIN SHUT·OFF DEVICE or RAIN SENSOR
A device which prevents the controller from activating the valves when a preset amount of rainfall is detected.

SMART CONTROLLER
An irrigation control system that uses weather-based calculations and environmental conditions to determine how much water to apply to a landscape based on the plant water needs.

SPRAY HEAD (SPRAYHEAD)
A type of fixed spray sprinkler that pops up from underground and waters a set pattern, usually from 4 to 15 feet in range. Used for lawns and shrubbery areas.

SOIL TYPE
The texture and structure of the soil particles which affects its ability to take in and store water for use by plants.  Soils range from clay to loam to sand.  Clay soils take in water more slowly than loam or sandy soils (lower infiltration rate).

SOLENOID
An electromagnet which is connected to a controller and causes the opening and closing of automatic control valves.

SPRINKLER
A hydraulically operated mechanical device which discharges water through a nozzle or nozzles.

STATION
A circuit on the controller which activates a single control valve in the irrigation system to control watering for a particular zone.

UNIFORMITY
How evenly water is distributed over an irrigated area.

VALVE
A valve is like a faucet. Valves respond to commands from the controller. When valves receive a signal to open, water flows to the sprinklers. when they receive another signal to close, the flow of water stops.

WATER BUDGET
A feature of Rain Bird controllers that let you easily change the run times of your sprinklers without having to reprogram the controller.  Use water budget to increase or decrease watering in response to changing seasonal needs throughout the year.

WATER HAMMER
A damaging shock wave created when the flow of water in a pipe system suddenly stops. Usually the result of a fast-closing valve.

WATER PRESSURE
The force which is exerted by water. (In the United States, usually expressed in pounds per square inch. Its metric equivalent is Bars.)

WINTERIZATION
The process of removing water from an irrigation system before the onset of freezing temperatures.  Necessary to prevent damage to the sprinkler system that can be caused by expansion due to freezing water in the pipes.

WIRE GAUGE
Standard unit of measure for wire size. The larger the gauge number, the smaller the wire.

WORKING PRESSURE
The pressure of the irrigation system during operation. Synonymous with Dynamic Pressure.

ZONE
A section of an irrigation system served by a single control valve. Zones are comprised of similar sprinkler types and plant material types with similar water requirements and soil types.