Rainwater Harvesting

Capture rain. Store it. Water your garden with it.

Rainwater you collect and store can provide a valuable source of irrigation water that isn't dependent on mains supply restrictions.

How the system works

Rainwater harvesting with pumped drip irrigation: a roof-fed tank, pump and multi-zone controller supplying three zones (ornamental beds, kitchen garden, lawn and trees), with key components shown: leaf filter and first-flush diverter, rainwater tank, pump with pressure control, multi-zone controller, mainline pipe, low-water float switch, filter, pressure regulator, solenoid valves and drip emitters.

What could your roof collect?

The calculation is simple: roof area × rainfall × a runoff efficiency factor (we use 0.8, accounting for typical filtering and overflow losses). Try your own numbers below.

For reference: a typical UK rain event is roughly 15–25mm. Sussex sees around 700–800mm of rain across a whole year.

1,600 litres collected, per rainfall event

Roof area × rainfall × 0.8 runoff efficiency. This is an estimate to size a system by — your actual assessment accounts for your specific roof, guttering and planting demand.

Rainwater first. Mains backup.

A Water Secure system draws from your stored rainwater automatically, and only calls on the mains supply if the tank runs dry — subject to your water company's rules and the correct backflow protection.

Worth knowing: harvested rainwater can generally be used for garden irrigation without an abstraction licence, where it consists solely of collected rainwater stored and used under the relevant conditions. Rules and exemption thresholds can change, so we confirm the specifics for your setup as part of your assessment rather than relying on a blanket statement here.

See what a rainwater system could do for your garden.

Free assessment, tailored to your roof, garden and water source.

Get A Free Irrigation Assessment