Glossary of Terms: Irrigation

Spray Arc: Describes how far around in a circular pattern a sprinkler will rotate or spray. A sprinkler with a 90° arc would spray a quarter circle.


Backflow Preventer: A device installed between the water supply and the sprinklers that is designed to prevent the backflow of contaminated water into the drinking water. Different areas of the country require different types of backflow preventers. Check your local regulations.


Cable: In an automatic irrigation system, low voltage Irrigation Cable or Wire is used to connect the automatic control valves to the controller. The most frequently used wire for the home sprinkler system is multi-core. Color Coded, multi-core sprinkler wire has several coated wires together in one protective jacket. It is a good idea to install extra wires for future expansion of the system.  You need a separate wire for each zone plus a shared common wire. For example 5 core cable  will suit a maximum of 4 zones (4 solenoid valves).


Controller: Also known as a timer, the part of an automatic sprinkler system that determines when a valve will turn on and how long it will operate. The timer sends a low voltage signal to the valve, which will then open for a predetermined amount of time allowing water to flow to the sprinklers. What size timer to purchase is determined by how many zones are in the sprinkler system.  For example a 4 zone controller will suit up to 4 zones or 4 solenoid valves.


Flow Rate: Expressed in LPM (litres per minute), volume is used to describe either the amount of water available or the amount of water used.


Friction Loss: Water flowing through the meter, valves, pipe, and fittings has considerable drag or friction. When the velocity of water increases, the friction loss increases. The friction reduces the available static pressure. The smaller the pipe the more friction loss and the less amount of available water to the sprinklers.


LPM (litres per minute): Your LPM is your flow. Not to be confused with pressure, the LPM of your water supply must be worked out before starting your irrigation system design. Different irrigation types have different LPM requirements. The total LPM specs of all sprinklers/drip tube on one zone must not exceed the LPM of the water supply.


Head-To-Head: This phrase describes the correct placement of spray heads and stream rotors. One sprinkler must be placed so that it will spray across to another sprinkler (or 50% of the adjusted diameter). This provides for complete coverage and prevents dry spots.


Lateral Pipe: Non-pressure pipe running from the valve to the sprinklers.


Low Head Drainage: Water left in the pipe after a valve is turned off that is gently flowing out of a low elevation sprinkler head. Usually leaves an annoying puddle.  The problem can be solved using sprinklers that have a check valve.


Main (Main line): Pressurised pipe running from the P.O.C. to the zone control valves.


Manifold: The pipe and fittings that join a group of valves joined together.  The manifold is on the inlet side of the solenoid valve and must always be in pipe suitable for pressure. Eg. PVC pipe.


Low Density Poly Pipe: Black, flexible pipe that is low cost, ideal for use as a lateral pipe but cannot be used in constant mains pressure applications. It is connected with barbed fittings & ratchet clamps. This pipe is used on the outlet side of the solenoid valve - never on the inlet.


POC - Point of Connection:  This is the join where the sprinkler system connects to the mains water.  There is usually an isolation valve (ball or gate valve) at this point. This enables the sprinkler system to be shut off while water is still turned on in the house.   It is also the ideal location for the backflow preventer and master valve if required.


Precipitation Rate: Expressed in centimetres per hour, precipitation rate is the rate at which water is being applied. Matched precipitation means all of the sprinklers in the area are placing about the same amount of water on a given area. Matching precipitation rates on a single zone is important or you will end up with uneven watering.


Pressure: Measured with a pressure gauge and expressed in Kilopascals (kPa). Static pressure is the kPa measured when no water is flowing through a closed system. Dynamic pressure is the kPa measured when the system is open, or water is flowing through.


Program: A program is information the user enters into the timer’s memory that determines when the system will water. Not to be confused with a start time on it’s own. A program for an automatic sprinkler timer contains three pieces of information: what days to water, what time to start watering all zones, and how long each zone will water.


PVC pipe: The most common type of pipe used in pressure applications. Generally white in color, PVC pipe is more rigid and requires the use of PVC solvents to join. The pipe manufacturers also recommend the use of primer just prior to the application of the solvent.

This pipe can be used on both the inlet and outlet sides of the solenoid valve.


Radius: How far out from the sprinkler the water sprays. A nozzle with a 17' radius means that the water will spray out as far as 17 feet (approx 5 metres). The radius is always measured in zero wind conditions.


Gear Drives (Rotors): Gear-driven sprinklers that shoot out a solid stream of water and rotate slowly in a circular pattern, streaming out water to areas as small as 17 feet (approx 5m) and as large as 75' (22.5m) or more.


Spray Heads: A sprinkler that emits a fan-type spray of small droplets of water. These heads have a radius of 17' (5m) and shorter. These nozzles can be fitted to Pop-Up Sprinklers or Risers.


Station (Zone): A term used when discussing controllers. Sprinklers in a watering zone are connected by pipe to a valve, which is wired to a station on the controller. Controllers are sized by how many stations they can operate. (eg: a 6-station controller can control from one to six valves)


Trench: Irrigation piping is commonly buried in trenches. To avoid future damage pipelines should be at least 15 to 20 cm deep.


Valve: In an irrigation system, there are many types of valves. Valves to prevent backflow, shut-off valves, solenoid valves and more. Most commonly, if an irrigation professional talks about a valve, they’re talking about a Solenoid Valve. That is what’s operated by the controller to automatically provide water to your garden.


Shut-off Valve: Come in 2 main types, Ball Valves & Gate Valves. Gate valves have a wheel type handle which requires several turns of the handle to turn off which means you have more control of flow. Ball valves have a single arm or lever that requires a quarter turn to turn on or off. This single action is convenient for easy fast shut-off, but caution should be used and the valve should not be turned on or off too quickly while water is flowing, as damage could result.


Solenoid Valves: Are used in conjunction with controllers to provide automatic irrigation to the garden.


Valve Box: A plastic box with a lid that is buried in the ground to house the solenoid valves.

These boxes protect the valves from damage and also make them easy to find if servicing is required.



Water Hammer: The surging of pressure which occurs when a control valve is suddenly closed. In extreme conditions, this surging will cause the 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 irrigation system, low voltage Irrigation Cable is used to connect the automatic control valves to the controller. The most frequently used wire for the home sprinkler system is multi-core. Color Coded, multi-core sprinkler wire has several coated wires together in one protective jacket. It is a good idea to install extra wires for future expansion of the system.  You need a separate wire for each zone plus a shared common wire. For example

5 core wire will suit a maximum of 4 zones (4 solenoid valves). 7 core - maximum 6 solenoid zones.


Zone:  A term used to describe an area of sprinklers that are connected together and controlled by 1 solenoid valve. For example the sprinklers connected together in the front lawn could be called Zone 1. The sprinklers in the fernery could be called Zone 2.


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