Glossary of Terms

Arc: Circular pattern a sprinkler will rotate or spray.

Backflow Preventer: A device installed between the P.O.C. and the control valves that prevent the backflow of contaminated water into the drinking water. Check with your Hunter dealer or local permitting agency for the device(s) approved for your area.

Check Valve: A small device often installed in the base of a sprinkler that allows water to flow in one direction only and does not open until a preset pressure is reached. Is usually used to prevent low head drainage and pooling of water at the bottom of a slope or low areas.

Control Valves: Automatic sprinkler control valves are valves that are activated with a low voltage output from the controller and are connected to the controller by direct burial low voltage wire. A group of control valves located together is called a manifold.

Controller (Timer): A device that uses low voltage connected via wiring to activate automatic control valves that open and allow water to flow to sprinklers for irrigation. The user sets the individual programs that consist of program start times, stations (zones or valves), run times, and watering days.

Drip Control Zone Kit: A kit that includes a control valve, a filter, and a pressure regulator for drip zones.

Friction Loss: Water flowing through the meter, pipe, valves, and fittings will have considerable drag or friction. When the velocity of water increases, the friction loss increases. When the diameter of the pipe increases, friction loss decreases. Friction loss reduces the available dynamic pressure. Head–to–Head: This phrase describes the correct placement of spray heads or stream rotors. One sprinkler must be placed so that it will spray another sprinkler (or 50% of the adjusted diameter). This provides for complete coverage and prevents dry spots.

MP Rotator: A high-efficiency, low-precipitation-rate, rotating stream spray nozzle that can be used in place of traditional spray nozzles.

P.O.C. (Point of Connection): Sprinkler mainline tie-in point. A manual shutoff valve is usually installed at this point to shut off the irrigation in the event of a pipe break or to perform maintenance on the system.

Poly Pipe: Polyethylene pipe is a black, flexible pipe popular in areas that are susceptible to long winter freezes. Insert or compressions fittings are used to connect the pipe.

Precipitation Rate: Expressed in inches/hr, precipitation rate is the rate at which water is applied. Matched precipitation means all of the sprinklers in the area are placing about the same amount of water in a given area. Different type of sprinklers should not be installed in the same zone. Large and small area sprinklers may have GLOSSARY OF TERMS similar GPM but the area they cover is not the same and the precipitation rates would be very different.

Pressure: Measured with a pressure gauge and expressed in PSI. Static pressure is the pressure when no water is flowing through a closed system. Dynamic pressure is when the system is open and water is flowing though the pipes.

PVC Pipe: The most common type of pipe in areas with warmer climates. Generally white in color, PVC (polyvinyl chloride) pipe is more rigid than poly pipe and uses PVC solvents to glue the pipe together.

Radius: Distance that the water sprays from the sprinkler.

Rotors: Gear-driven sprinklers that deliver a solid stream of water and rotate slowly in a circular pattern, from 15'–46'. Rotors fit into the “large-area sprinklers” category.

Sensor: Weather–activated shutoff device. Shutoff Valves: Valves are used to isolate the irrigation system from the water supply or to isolate sections of the irrigation system for maintenance. The valve may be either a brass gate valve or a brass or plastic ball valve. Care should be used to slowly turn ball valves on or off as they only require a ¼-turn to open or close and could cause damage if operated too rapidly.

Spray Heads: Sprinklers that emit a fan–type spray of small droplets of water. The heads have a radius of 17' of less. Spray heads fit into the “small-area sprinklers” category.

Volume: Expressed in GPM (gallons per minute). Volume is used to describe either the amount of water available or the amount of water used. The available gallons per minute must be known before a sprinkler design can be completed. The total GPM of all the sprinkler heads on one zone should not exceed the available GPM.

Water Hammer: The surging of pressure that occurs when a control valve is suddenly closed. In extreme conditions, this surging will cause pipes to vibrate or create a pounding noise. Water hammer is most commonly caused by fast closing valves or pipes that have been sized too small, causing high-velocity water flow.

Wire: In an automatic sprinkler system, a low-voltage direct burial wire is used to connect the automatic control valves to the controller. Color-coded, multi-strand sprinkler wire is the most common and has several coated wires together in one protective jacket.