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Glossary of Sprinkler System and Irrigation Terms


100% Coverage:   The design goal of all sprinkler system designs. Frequently used incorrectly in place of the term "head to head coverage". 100% coverage is the objective of head-to-head coverage. But head-to-head coverage does not always result in 100% coverage. See our page on Head to Head coverage for pictures and a full explanation.

Arc: The percentage of a circle that sprinkler head covers. 90º is a quarter of a circle. 180º is half a circle. 360º is a full circle.

Acre Foot: (also acre feet)   The amount of water needed to cover one acre of area with water one foot deep.  Most often used for agriculture/farming.

Acre Inch:   The amount of water needed to cover one acre of area with water one foot deep. Most often used for agriculture/farming.

Angle Valve:  The valve outlet is on the side and the valve inlet is on the bottom. Refers to the water flow pattern into and out of the valve. A more reliable and lower friction loss alternative to globe valves. Frequently used as control valves. Infrequently used as isolation valves.  

Anti-Siphon Valve:  A control valve with a built-in atmospheric vacuum breaker (back-flow preventer). Most often used in residential irrigation systems.

Application Rate: The measurement of the volume of water applied to lawn in a given time. Frequently referred to as inches per week.

AVB - Atmospheric Vacuum Breaker:   A type of backflow preventer. Prevents water - and lawn chemicals - from the sprinkler system from siphoning back into the water supply.  A backflow preventer is required by most cities

Audit or Irrigation Audit:  a detailed review of and irrigation or sprinkler system which includes identification of problems that should be corrected and suggested solutions. Will also include suggestions for ideal watering schedule.

Automatic Valve:    A remotely operated valve. Automatic valves are commonly used as control valves. Most frequently used as control valves.

AWG-UF: Classification of the electrical wire used for automatic sprinkler systems. E.g. 14-1 AWG-UF means a 14 gauge wire, single wire cable, designed for direct burial - no conduit. All wires should have this information printed on the wires insulation.

B - C
Backflow Preventer: A device that prevents contaminated water from being pulled back into the water source should a reverse flow situation occur. (Which happens more a lot!) In most states backflow preventers are required by law on all newly installed irrigation systems.

Ball Valve: This style 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 through the valve with little 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, and they tend to be very reliable and trouble-free.

Brass Nozzles:
Less frequently used, they are a step up from plastic nozzles. They are very long lived, more expensive, and a bit more precise in water delivery. Plastic nozzles are the most common, cheaper and and work fine

Bushing:  A bushing is a small piece used to connect two pipes of different sizes together. A standard reducer bushing has one male end and one female connection.

Butterfly Valves:  This type of valve uses a rotating disk to control the water flow. Butterfly valves are used as both isolation and control valves. Butterfly valves tend to be very reliable. They are mostly used on larger pipe sizes. Ball valves are used on smaller size pipes.

Clock: another term for controller or timer or control box.

Booster Pump:  A device to increase the water pressure is a system where some pressure already exists, and you would use a booster pump to increase the pressure.

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.

Controller: A clock, control box or timer used to control 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 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".

Cubic Meters: A metric measurement of water quantity, 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.

Cycle and Soak: Breaking the watering cycle into shorter segments allowing the water to soak into the ground between cycles. Example: Watering for 5 min and then letting it soak for 2 hours and watering for an additional 5 min is more effective than watering for 10 min straight.

D - G
Design Pressure: Usually referring 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 operating.

Drip Irrigation: An irrigation system that applies water directly to the soil slowly, hence the name "drip" irrigation. The most efficient irrigation system in terms of water and energy use. Best used for plants and shrubs.

Drip System: An irrigation system that uses drip irrigation.

Elevation Head: A measurement of pressure.

Ell: A fitting used to change the direction of a pipe.  You can remember ells simply by their shape, they look like an "L".   PVC 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 with barbs, or barbs and barbs.

Emitter: A term used with drip irrigation. The emitter, or drip bug is a small device that controls the flow going to the soil. Emitters come in many different flow rates and styles.
ET (Evapotranspiration): Amount of water lost due to evaporation from heat and use by plants. ET is used by Rainbird Smart Controllers to help determine the amount of watering needed by lawns and plants.

Female Adapter: A fitting used to adapt from  glued PVC to a threaded or barbed connection. Never, ever use a plastic female adapter on anything with metal threads.  The female adapter will split if you over tighten it or use too much Teflon tape.
Flex Pipe: A flexible pipe usually ½" in diameter that is used for swing joints on pop-up spray heads and rotaries. Allows the pipe and head to flex rather than breaking.
Flow: The movement of water
Flow Sensor: A device which actively monitors the amount of water moving through a pipe.

Fittings: The generic name for the various parts that attach the pipes together, including; bushings, couplings, crosses, ells, female adapters, male adapters, reducers, and tees. Fittings may or may not be 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.) Avoid 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.  Gate valves wear out fast when used often. They are not designed for regular use, but for emergency shut-off only.
Gear Driven Rotary Heads: provide a consistent powerful rotation for sprinklers systems. Water enters the base of the head and moves through a diffuser that converts it into high velocity jets. These jets are then hit a turbine-like rotor causing it to spin at high speed. The gear train then reduces the high rotational speed and converts it into higher turning torque. Torque gives the nozzle assembly the relative slow rotational speed and consistent coverage.

Globe Valve: Refers to the water flow pattern into and out of the valve. Often used as control 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 reliable, but have slightly higher friction loss than "angle" valves, the other common style used for control valves.

GPM: Abbreviation for Gallons Per Minute

Gravity Flow: The term given a water system that relies on gravity to provide the pressure required to deliver the water. Consists of a water source located at a higher elevation than the water delivery points. Kiowa is a good example should you ever drive out there.

Head:  Short for "sprinkler head".

Head to Head:  In irrigation "head to head" refers to the situation where sprinklers are spaced so that the water from one sprinkler covers all the way to the next sprinkler. All sprinkler systems should be designed to give head to head coverage, as the best performance is achieved when this spacing method is used.

Hydro-Zone: An area of an irrigation system where all the factors that influence the watering schedule are similar. Typical factors are the type of plants, the precipitation rate of sprinklers or emitters, solar radiation, wind, soil type, and slope.
Impact Rotary Sprinklers: Employ a weighted, spring-loaded drive arm to create the force to rotate the nozzle. The sprinkler system spray deflects the arm and the spring pulls the arm back into the path of the sprinkler spray. As the drive arm completes a cycle it impacts against the nozzle assembly rotating it slightly.

Isolation Valve: A valve used for isolating all or part of the irrigation system for repairs, maintenance, or winter shut-down (winterization).

Lateral: The name given to the pipes which go from the control valves to the sprinklers or drip systems.
Low Head Drainage: Flow from low-elevation sprinkler heads in a sprinkler system after the control valve has been closed. Often gravity induced.
Master Valve: A valve used to protect the lawn from flooding in case of a ruptured main or malfunctioning downstream valve. The master valve is on the mainline (after the backflow preventer and the control valves).

Main (Mainline): The Pipe(s) going from the main water source to sprinkler control valves.

Male Adapter: The fitting used to adapt to a male threaded end. When connecting to metal threads male adapters should be used, so that the plastic male threads screw into the metal female threads.
Moisture Sensor: A device which measures the amount of moisture in the ground. Frequently used as Rain Monitors which shut off your system during or after rain.

Nipple: A common plumbing term for a short length of pipe threaded on both ends.

Nozzle: The part of a sprinkler head that the water comes out of.  An engineered part that assures a good spray pattern. In most cases the nozzle is removable so that it can be easily cleaned or replaced. With plastic nozzles replacement is generally preferred over cleaning as small scratches in the plastic can cause big problems with water distribution and uniformity.

Operating Pressure: The pressure at which a device or irrigation system is designed to operate. There can be "optimum operating pressure", "minimum operating pressure" or a "maximum operating pressure".
Overspray: Water which is being wasted by being sprayed to an undesirable location. Examples include spraying the side of your house, the street or the neighbors lawn.


Polyethylene: A plastic used for manufacturing lawn sprinkler irrigation tubing. "Poly" for short. Poly pipe is almost always black in color.  It is very flexible, and is usually sold in coils of 100 or 300 feet. Poly pipe uses insert type fitting, with pinch clamps. Exception- special barbed fittings 3/8” flexible tubing.

Poly Vinyl Chloride: The real name for PVC pipe.

Pop-Up Sprinkler Head: A sprinkler head that retracts to ground level when it is not operating. Pop-up sprinklers which stick in the raised position need to be replaced before the lawn mower breaks them.

Precipitation Rate: A measurement of water application. The measurement is given in the depth of water applied to the soil.
Pressure Gauge: A device used to measure water pressure. The best pressure gauges are "liquid filled".

Pressure Vacuum Breaker (PVB): A type of backflow preventer. Prevents water - and lawn chemicals - from the sprinkler system from siphoning back into the water supply. A PVB is required by most cities.

Pressure Loss: The amount of water pressure lost as the water flows through the sprinkler system. Pressure is primarily lost due to friction and gravity.

PSI: pounds per square inch - Used to define pressure.

Pump: A device which increases the water pressure or moves water.

PVC: Abbreviation for poly-vinyl-chloride. A type of plastic used to make water pipe. Usually white in color but sometimes is gray, brown, tan, or purple. If it's purple it means use only for "reclaimed water"- don't drink the water in it!

Reduced Pressure Assembly (RPA): Backflow Preventer that knocks down high pressure water feeds.

Reducer: A fitting used to change from one size pipe to another. Two types are generally available. The first, and most common is the reducer bushing. The reducer bushing fits inside a coupling or another fitting on the large end. The pipe fits into the reducer bushing on the small end. The other common reducer is a "bell reducer". The pipe fits inside the reducer on both ends of the bell reducer.

Risers: Pipe and sprinkler heads that stands permanently out of the ground. Used for even water distribution above taller shrubs. Frequently made out of Schedule 80 gray PVC. Can also be made out of copper for a classier look.
Rotary Sprays: Rotary pop-up sprinkler heads. These can be impact or gear driven. Most commonly used for large turf areas.
Rotary nozzle: Rotary nozzles replace fixed spray nozzles and use less water than, but they require longer watering times.
Run Off: Water which is not absorbed by the soil and drains off in the street or low area in the yard. Run-off occurs when water is applied in excessive amounts or too quickly for the soil to absorb.
SCH 40: Schedule 40 PVC pipe. The standard for pipe diameter and wall thickness used for plastic and steel pipe.
SCH 80: Schedule 80 – see above, only stronger.
Shrub Sprinkler Head: A sprinkler head mounted above ground level on a pipe or riser.  Usually used for watering shrubs.

Slip: Slip is the term used to describe a solvent welded connection on a fitting.
Socket: A socket is a female connection on a fitting. It can be threaded, or glued, but most of the time the term is used for glued fittings.

Spigot: A spigot is a male connection on a fitting. A spigot fits inside a socket. It can be threaded, or glued, but most of the time the term is used for glued fittings.

Spring: The coiled metal device that retracts a sprinkler head or helps a hydraulic valve close.

Sprinkler: Used for watering residential and commercial lawns, plants. Also used for agricultural irrigation.

Square Spacing: A sprinkler head layout where the sprinklers where there is one sprinkler head in each corner of the square. Triangular spacing is more efficient.

Static Water Pressure: The water pressure as measured when the water is not moving. When measuring the static water pressure all the water outlets on the pipe must be closed.


Tee (Tee Fitting or T Fitting): A Tee is a fitting used to branch a side pipe off of a pipeline. Shaped like the letter "T". A related fitting is the "Y" fitting which is used primarily for sewer pipelines and not sprinklers.

Triangle Spacing: The term given to a sprinkler head layout pattern where the sprinklers, when viewed from above, appear as a more or less equilateral triangle with one sprinkler in each corner. Triangular spacing leads to the most uniform and efficient water application using sprinklers.

Trickle Irrigation: Another name for drip irrigation.

VAC: Volts Alternating Current. Most electric control valves operate on 24 VAC.
Valve: A device used to control the flow of water. Control valves turn on and off the water to the individual circuits of sprinklers or drip emitters.
Valve Box(es): The underground boxes in your yard, allowing access the valves in the event of a repair. You will likely never need to access these yourself.

Valve Zone: An area where the irrigation is all controlled by a single control valve.

Variable Arc Nozzles: Allow for adjustment of the spray arc or pattern by twisting the collar to the desired position. Best for curved bed and turf areas.
Water Hammer: The damaging shock wave caused when the flow of water in a pipe system suddenly stops. Often the result of a fast-opening valve.

Water Meter: A device used to measure the quantity of water that flows through a pipe.

Water Table: The top of an underground aquifer or the "groundwater" level.

Winterization: The process of removing water from a sprinkler system with high pressure air before the first hard freeze of winter. ESSENTIAL to prevent damage to the sprinkler system. Damage is caused by expansion due to water freezing and expanding in pipes.

Zone: A section of a sprinkler/irrigation system served by an individual control valve. Zones are comprised of similar sprinkler types and plants that have similar watering requirements and soil types.
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