The space between the bottom of the water inlet into a tank, and the maximum possible water level of the tank. For irrigation the air gap must be ‘Type AA’ or ‘Type AB’. Distances for the gap are laid down by the WRc. Provides category 5 back siphonage protection.

Air Valve

Device to let air into the system when there is a negative pressure. Used to prevent siphoning.

Ball valve

Refers either to:

a)A float on an arm which closes the inlet valve to the tank when the water level has risen to its desired level. Access Irrigation supply floating ball valves

b) A tap with a drilled ball inside, providing an unrestricted flow when open. Ball valves go from fully open to fully closed in a 90 degree turn. Access Irrigation supply threaded ball valves and glued ball valves .

Bar

A unit of pressure. 1 bar is approximately equal to 10m head or 14.5058 p.s.i (pounds per square inch). 1 bar is also approximately equal to 1 atmosphere.

Barbed fitting

A plastic pipe fitting which pushes into the pipe. Barbs of the fitting prevent the pipe being pushed off the fitting by the water pressure. Only suitable for lower water pressures using soft walled LDPE pipe. Barbed fittings are available from our on-line shop.

Battery controller

Battery powered irrigation timer, often fitted to an outside tap in gardens, used to automatically turn on and off the irrigation. Access GArden Products supply a range of tap timers for gardeners.

Bib Tap

Outside tap with a thread on to allow the connection of hoses. Also known as a hose union tap.

Byelaws

Water company byelaws have now been superseded by the Water Supply (Water Fittings) Regulations 1999 in England and Wales. The byelaws, however for the basis of these new regulations.

Calmed Inlet

Device fitted at the bottom of a rainwater tank to prevent disturbance of the sediment layer.

Compression fitting

A pipe fitting which clamps around the pipe end and is tightened using a knurled nut. Designed for use with MDPE polythene pipes up to 12 bar pressure rating. Access Irrigation supply a range of compression fittings in sizes 16mm - 63mm.

Control panel

A unit (usually electronic) which automatically operates the irrigation system, usually on a timed basis. Also known as a panel.

Glossary of Irrigation terms: D-H

DB Valve

Backflow prevention device required by the Water Regulations for irrigation in House Garden situations where the emitter is below 150mm off the ground. Provides category 4 back siphonage protection. DB valves are available from our on-line shop.

Decoder

A computerised unit which fits on to a solenoid valve. Instead of being hard wired to the control box, all the solenoids are linked by just a 2 or 3 core cable. The controller then sends messages to each decoder telling it to turn on the valve.

Dilutor

Low cost device for adding fertiliser to the water flow utilising a venturi and a pressurised fertiliser bottle. Brands include Access Dilutor , Cameron Dilutor, Keylutor, Bagley Dilutor

Double check valve

Required for all hose union taps in ‘House Garden’ installations. Type EC double check valves provide category 3 back siphonage protection.

Drip line

Polythene pipe with drippers either mounted inside the pipe (inline drip) or on top of the pipe (online drip).

Drip tape

Very thin walled drip irrigation lines used in horticulture and agriculture to water row crops. Often the drip tape is laid and lifted with the crop. Well known brands include t-tape , aqua-traxx, queen gil

Dripper

Low flow emitter with flows typically between 1 l/h and 8 l/h. Designed to drip water at low pressure onto the compost. Well known commercial brands include Netafim , Naan, NaanDan

Emitter

Outlet through which water is designed to flow. Also known as a nozzle, sprinkler or dripper.

Field Capacity

A measure of the soils ability to hold water. The amount of water added by the irrigation should not exceed this amount, otherwise puddling and run off will occur.

Filter

Added to an irrigation system to prevent debris and dirt entering the system and blocking the outlet holes of sprinklers and drippers. There are a number of filter types including sand filters, gravel filters, screen filters, disc filters, leaf filters (for rainwater harvesting systems) and self-cleaning filters. Access Irrigation sell a range of filters on-line

Friction loss

Term used to describe the loss in pressure when water flows along a pipe. For any given flow the larger the pipe, the lower the friction loss.

Geka fitting

Brand of quick coupling used in horticulture to couple hoses together. Bayonet design allows quick assembly of hoses together. Access Irrigation supply a range of geka type fittings compatible with the original geka design.

Heat Mat

Modern version of soil warming cables that produce gentle root zone heating.

Hose

Very flexible water pipe used to transport water. Often coloured green in domestic gardens and yellow in nurseries and garden centres. Popular sizes are ½” (12mm); ¾” (19mm) and 1” (25mm). Well known brands include Tricoflex.

Glossary of Irrigation terms: I-O

Injector

A pump, either water or electrically powered, which adds chemicals (usually fertilisers) into the water stream. Well known brands include Dosmatic, Dosatron.

Lance

Hand watering device with a watering rose on one end and a valve at the other. Used for hand watering, especially in horticulture. Hand watering lances are available from Access Irrigation Ltd.

Latching Valve

Solenoid valve designed for use with battery operated controllers. The valve is opened and closed using a single pulse of power.

L.D.P.E. pipe

Low density polyethylene (LDPE) - the grade of pipe used for above ground irrigation pipe. The pipe is coloured black to resist the effects of sunlight, and has a soft wall to allow fittings to be punched into the side. Low density pipe is available from the Access Irrigation online shop.

Leaky pipe

The trade name for a porous pipe which can be buried underground. The emitter holes are so fine they resist the intrusion of roots. The name is often used generically to describe any type of trickle line.

Level switch

A switch which is triggered by the rise or fall of the water level in the tank. This can be used to prevent the tank running dry. Also known as a float switch.

L.P.H.

Litres per hour (also l/h). Metric measure of flow, 1,000 l/h is equal to 1 m3/hr (meter cubed per hour)

Manifold

A set of solenoid valves linked together, each providing water to a separate zone on the irrigation system.

M.D.P.E. pipe

Medium density polyethylene (MDPE) - the grade of pipe used for mains water pipe and irrigation pipe. Potable water pipe is normally coloured blue and irrigation pipe black. Access Irrigation supply MDPE pipe in a range of coil sizes.

Mist Propagation

System for rooting cuttings and germinating seedlings using soil warming cables (or heat mats) a mist nozzles. The propagation system often uses a ‘wet leaf’ sensor to control the mist cycling. A number of mist propagation kits are available on-line.

Mist Wean controller

Mist propagation controller with a built-in weaning function to allow seedlings to be weaned off their dependence in the mist.

Multi-core cable

A many stranded cable linking the solenoid valves to the controller. Each valve has a separate core of cable connecting it to the controller, in contrast to a decoder system.

Nozzle

Another phrase for an emitter

Octamitter

Simple dripper which allowed the output to be varied by twisting the top cap

Glossary of Irrigation terms: P-S

Pop-up sprinkler

A sprinkler which is buried under the turf level which rises up out of the ground to water the area. It then retracts out of the way of mowing machines. Well known brands include Hunter, Toro, Rainbird. Hunter pop-up sprinkler s are available from our on-line shop.

Pressure compensated

A drip nozzle designed to give a uniform output regardless of the pressure. Output will vary with pressure on non-compensated nozzles. A wide range of drip nozzles are available from Access Irrigation.

Pressure regulator

Device for ensuring a constant pressure in the irrigation system

Pressure vessel

A container holding pressurised water. By holding a reservoir of water under pressure, the number of start/stop cycles on the pump is reduced.A range of pressure vessels in available from Access Irrigation.

Pressure-stat

A mechanised pressure switch which starts the pump when the pressure drops below a pre-set level.

Pump

Designed to provide pressure in the irrigation system. Irrigation pumps tend to be mainly electrically powered centrifugal pumps in either horizontal or vertical in configuration. Multi-stage pumps feature a number of separate chambers to increase the water pressure. In agriculture petrol or diesel pumps tend to be used. Well known brands include Espa , Grundfos and DAB

Pump and tank set

A water storage tank and pump in one unit to save space.

Pump budget

When the system is designed a requirement for the pump will established. This will include the maximum pressure (head) required and the maximum flow.

Pump inverter

Electrical device for varying the speed of the pump to provide a constant pressure. Pump wear is reduced as the pump is not always running at full speed. Access Irrigation provide a range of pump inverters .

R.P.Z. valve

Reduced pressure zone (RPZ) valve. A mechanical device that can be used to replace a type A air gap in some circumstances. Provides category 4 back siphonage protection.

Rain Sensor

Designed to detect rainfall and reduce the irrigation cycle. Simple units are manufactured from expanding discs, while more sophisticated units measure actual rainfall.

Rainwater Harvesting

Method of capturing and storing rainfall for use in irrigation systems and toilet flushing.

Riser

Irrigation pole made from metal or plastic for mounting sprinklers above ground level.

Shrub head sprinkler

Derivation of a pop-up sprinkler where the sprinkler head does not rise up on operation. Used above ground, often in shrub borders.

Solenoid valve

An electrically operated tap, which opens and closes under the control of the irrigation panel. Usually operated at 24v AC for safety. Well known brands include Bermad, Toro, Hunter. See also latching valve.

Sprinkler

Emitter with higher water flows which uses the pressure from the water to shatter the water into small droplets and throw them a distance from the emitter. Outputs and coverage can vary depending on the design.

Starter box

A relay or contactor that brings the pump on, usually controlled by the irrigation panel.

Glossary of Irrigation terms: T-Z

Travelling sprinkler

Water powered sprinkler that moves along as it waters. Small versions have spiked wheels and travel along the hose, larger versions have a steel wire that is attached to a fixed point and in reeled in by the unit. Used to water sports pitches, football pitches and rugby pitches. A range of travelling sprinklers is available online from Access Irrigation Ltd.

Trickle line

Alternative name for drip line.

Turbulent flow A design of dripper which reduces blockages in dripper nozzles. Turbulence created by the maze design of the nozzle slows the waters flow, allowing a wider, less blockage prone passageway to be used.

UPVC Pipe

Grey hard walled pipe used for above ground installations such as glasshouse sprinklers systems. Prone to frost damage.

Vacuum relief valve

Prevents dirt being drawn into the drip pipes when the system is turned off. Frequently used on drip tapes and drip lines in contact or beneath the soil.

WRc

Water research council. The body involved in specifying and approving fittings for use in the water industry.

Water Regulations

Properly knows as “Water Supply (Water Fittings) Regulations 1999 ” is the act of parliament that covers the use of mains water in irrigation in England and Wales.

Warning pipe

An ‘overflow’ pipe situated below the top level of the tank or the weir. This pipe must be easily visible to show that the valve into the tank is leaking.

Weir

A large overflow on a type ‘AB’ overflow put into a tank to comply with the Water Regulations. Provides category 5 back siphonage protection. See also warning pipe.

Zone

Sections that the irrigation system is divided into. Systems are zones to account for different watering requirements, and also to reduce the size of the pump and pipework by reducing the amount of water used at any one time.

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