Garden irrigation systems

Drip irrigation delivers water slowly to the base of each plant through small emitters or a dripline laid under mulch. It uses far less water than sprinklers, because little evaporates or lands on paths. It suits borders, hedges, vegetable beds and pots.

Pop-up sprinklers are buried in lawns and rise when the water is on. They are designed in zones so that each area gets even coverage, and the water pressure and flow available at your tap decide how many heads can run at once. Sprinklers waste more water, especially in wind or midday sun, and they are more likely to be affected by restrictions in a drought.

The controller runs the zones on a timetable. Many can adjust to rainfall or soil moisture, which avoids watering in the rain. Controllers need a power supply outdoors or in a garage; a new outdoor circuit is electrical work for a qualified electrician.

In England and Wales, the Water Supply (Water Fittings) Regulations 1999 require you to give the water company notice before installing a garden watering system unless it is designed to be operated by hand, and to wait for its consent. The company has ten working days to refuse or attach conditions; if it does not respond, consent is treated as given. The same regulations require notice for water pipes laid outside a building at less than 750mm or more than 1350mm below ground. In Scotland, Scottish Water has equivalent byelaws.

The point of the rules is backflow. If a sprinkler head sits in a puddle of dirty water or fertiliser, and the mains pressure drops, that water can be drawn back into the drinking water supply. An automatic system needs backflow protection suited to that risk. An installer who knows the rules will include the right device and handle the notification; ask who does it.

• a plan of zones, emitters, sprinkler heads and pipe runs
• a water pressure and flow test at the supply point
• the backflow protection device and where it is fitted
• notification to the water company and who submits it
• the controller, sensors and power supply
• drain points and how the system is winterised
• a handover showing how to change the programme

Source: legislation.gov.uk · legislation.gov.uk

When water is short, water companies in England and Wales can impose temporary use bans. One of the uses that can be banned is watering a garden using a hosepipe, and the law says that includes anything designed or used for the same purpose. An automatic sprinkler system can therefore be caught. Each company's ban notice sets out its exceptions, and some types of system, such as drip irrigation, may be treated differently. Check the current notice for your area; do not assume an automatic system is exempt.

This is one reason to design for low water use: drip rather than spray where possible, a rainwater supply for part of the garden, and mulched beds that hold moisture.

Rainwater from the roof can supply part or all of an irrigation system. Linked water butts are simple and cheap; an underground tank with a pump holds much more and can feed a controller. A rainwater system must be kept completely separate from the mains supply, with no connection between them. Where a mains top-up is included, it needs the right type of air gap. The installer should label rainwater pipes and outlets so nobody drinks from them.

Water left in pipes and valves over winter freezes and splits them. Most systems need draining or blowing out before the first hard frost, and restarting in spring. Ask whether the installer offers this as a service and what it costs.

The usual mistakes are designing sprinkler zones without testing water pressure, so the far heads barely reach; putting shrubs and lawn on the same zone, so one is overwatered; and leaving the controller on a summer programme into autumn. Driplines buried too deep under mulch can also be cut by the next person digging the border. A plan of where pipes run is worth keeping with the house documents.

Tell us what you want to water, the size of the garden and whether there is an outside tap or a rainwater tank. After you confirm your phone and email, we offer the request, without your personal details, to landscapers and irrigation installers in the area. One firm can buy it. We email you its name, address and phone number before it sees yours. Using Offrano is free, and you are not bound to accept the quote. Ask the firm how it deals with the water company notification.