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Acre Foot (also acre feet) - A measurement of water quantity most often used in agriculture. The amount of water needed to cover one acre of area with water one foot deep. See the irrigation formulas web-page for conversion of acre feet to other measurements.

Acre Inch - See "acre foot" above and substitute "inch" for "foot".

Angle Valve - Refers to the water flow pattern into and out of the valve. Often used as control valves. Seldom used as isolation valves. The valve inlet is on the bottom of an angle valve and the outlet is on one side. Angle valves as a group tend to be very reliable and have lower friction losses than "globe" valves, the other common style used for control valves.

Anti-Siphon Valve - A control valve with a built-in atmospheric vacuum breaker (backflow preventer). Most commonly used in residential irrigation systems.

Atmospheric Vacuum Breaker (AVB) - A type of backflow preventer. See the Backflow Preventer.

Automatic Valve - A valve which can be remotely operated. The remote operation method may be either electrical (the most common) or hydraulic. Automatic valves are commonly used as "control valves" for irrigation systems. (See "valves".)

AWG-UF - The classification of the direct burial wire used for automatic sprinkler systems. Example: #14-1 AWG-UF means a 14 gauge wire, single wire cable, designed for direct burial (no conduit) in the ground. The wire should have this information stamped or printed directly on the wire's plastic insulation. The wire should be at least 18" deep for safety (in most areas this requirement is written into local law).

Backflow Preventer - A device that prevents contaminated water from being sucked back into the water source should a reverse flow situation occur. In most places backflow preventers are required by law on all irrigation systems.

Ball Valve - This type of valve controls the water by means of a rotating ball with a hole through the center of it. When the hole is aligned with the water flow the water flows freely through the valve with almost no friction loss. When the ball is rotated so that the hole is not aligned the flow is completely shut off. Ball valves are used primarily as isolation valves. They tend to be very reliable and trouble-free. Ball valves as a group tend to require more effort to turn on and off than other valves. For larger size pipes butterfly valves are usually used rather than ball valves.

Booster Pump - A device to increase the water pressure is a system where some pressure already exists. For example, if water comes from a water company at 40 PSI of pressure but you need 80 PSI of pressure for the irrigation system, you would use a booster pump to increase the pressure.

Bushing - A bushing is a small piece used to connect two pipes of different sizes together. A standard reducer bushing has one male end (for the larger pipe) and one female connection (for the smaller pipe).

Butterfly Valves - This type of valve uses a rotating disk to control the water flow. A true butterfly valve has two half-disks, hinged together in the center. When the disks, or "wings" are folded together the water flows freely past them. When folded out into the water stream the wings block the flow. Most "butterfly valves" are really "rotating disk" valves. They have a single, round disk that rotates on an axle. When fully open the disk is rotated so that it is aligned with the water flow. To close, the disk is rotated at a right angle so that it fully blocks the flow. Butterfly valves are used as both isolation and control valves. Butterfly valves tend to be very reliable and trouble free. They are mostly used on larger pipe sizes, seldom less than 3" in size. Ball valves are used on smaller size pipes.

CL 125, 160, 200, 315 - Pronounced "class-one-twenty-five", "class-one-sixty", "class-two-hundred" and "class-three-fifteen". Based on standard dimension ratios. Simply, CL 125 pipe is rated for 125 PSI working pressure, CL 200 for 200 PSI, etc. Most industry professionals will tell you that it's not wise to use pipe rated at less than twice the actual maximum water pressure level. In other words, for a water pressure of 100 PSI use at least CL 200 pipe.

Controller - A "timer" used to turn on and off an automatic irrigation system. Controllers range from very simple to extremely sophisticated computer systems that utilize modems, cell-phones, or radios and allow 2-way communication between the controller and the units (valves, meters, weather stations, soil moisture sensors, etc.) being controlled.

Coupling - A fitting used to join two sections of pipe together.

Cross - A fitting that joins 4 sections of pipe at one point forming a "cross". Reducing crosses are available which have different size outlets. Unless you order a custom made cross the outlets opposite each other are always the same size.

Cubic Feet - A measurement of water quantity, often used by water companies in the United States of America to measure water use by customers. A cubic foot is one foot in length, one foot in width, and one foot deep.

Cubic Meters - A metric measurement of water quantity, often used by water companies to measure water use by customers. A cubic meter is one meter in length, one meter in width, and one meter deep.

Design Pressure - The total pressure available to operate the irrigation system. Other uses of the term vary, but usually refer to the operating pressure at which a specific piece of irrigation equipment is designed to operate.

Draw Down - The depth (from the top of the well) to the water in a well when the pump is operating. The water level typically drops when the pump is running.

Drip Irrigation - Any type of irrigation system that applies water to the soil very slowly, thus the name "drip" irrigation. Currently the most efficient irrigation technology in terms of both water and energy use.

Drip System - An irrigation system that uses drip irrigation. See drip irrigation above.

Elevation Head - A measurement of pressure. Typical usage: "If you want to know more about elevation head you'll need to see the glossary definition for pressure head."

Ell - A fitting used to change the direction of a pipe. For PVC and poly irrigation uses they are available in 90 degree and 45 degree bends. Some specialty ells are available in other angles but have limited availability. You can remember ells simply by their shape, they look like an "L". PV C ells are available with threads in both ends, threads in one end and a glued socket in the other, or with glue sockets in both ends. Insert ells come with male threads and barbs, female threads and barbs, glue sockets and barbs, glue spigots and barbs, or barbs and barbs.

Emitter - A term used with drip irrigation. The emitter, or dripper, is a small device that controls the flow going to the soil. Emitters come in many different flow rates and styles.

Female Adapter - A fitting used to adapt from solvent welded PVC to a threaded or barbed connection. Never, ever use a plastic female adapter on anything with metal threads. Never tighten a plastic female adapter with a wrench, hand tighten it only. The female adapter will split if you over tighten it.

Fittings - The generic name for the various parts that attach the pipes together. Includes bushings, couplings, crosses, ells, female adapters, male adapters, reducers, and tees. Fittings may be threaded, barbed, soldered, or welded to the pipe. (The glue or cement used on plastic fittings is a solvent which results in a welded joint.) Plastic fittings with threads should never be tightened with wrenches. Hand tighten them only.

Gallons per Minute - A measurement of water flow primarily used only in the United States of America.

Gate Valve - Refers to the operating mechanism for the valve, which is a sliding gate which moves up or down to block the flow. Often used as isolation valves. Never used as control valves. Because the gate slides it is very subject to wear, and gate valves wear out fast when used often. Some gate valves use a wedge-shaped gate which holds up better. They are still not designed for regular use, but for emergency shut-off only.

Globe Valve - Refers to the water flow pattern into and out of the valve. Often used as control valves. Seldom used as isolation valves. The valve inlet is on one side of the globe valve and the outlet is on the other side. Globe valves as a group tend to be very reliable, but have slightly higher friction losses than "angle" valves, the other common style used for control valves.