Understanding the idea
Rainwater capture can reduce reliance on treated mains water for appropriate uses. The useful volume depends on roof size, seasonal rainfall, collection losses, storage capacity and demand.
Five practical steps
- Map your catchment. Measure only the effective roof surface draining into your selected gutters and downpipes.
- Estimate potential yield. Multiply roof area in square metres by annual rainfall in millimetres and a realistic collection efficiency. One millimetre falling on one square metre is approximately one litre.
- Plan storage, overflow and dry spells. A large annual yield is not the same as water available in August. A safe overflow route and realistic tank capacity matter.
- Check water quality. Roof runoff may contain microorganisms or contaminants. Use suitable filtration and testing for the intended use, especially edible crops and aquaculture.
- Maintain and learn. Inspect gutters, screens, tanks and levels; record actual rainfall and consumption.
What to check
Illustrative figures do not guarantee usable water. Water collection, treatment and discharge must suit the site and intended use.
Healthical guide — general educational information. Assess local ecological, legal, hygiene and safety circumstances before building or planting.