Plants do well on rainwater, and it costs you nothing. A water butt on a downpipe is one of the cheapest upgrades for any garden, and a greenhouse roof can fill one too.
How much rain can you collect?
The sum is simple: 1 mm of rain on 1 m² of roof gives you 1 litre of water. A shed or greenhouse roof of 5 m² collects 50 litres from 10 mm of rain. A house roof collects many times more.
What size water butt?
- Around 100 litres: for a small garden or a tight spot, often in a slim shape against the wall.
- Around 200 litres: a common size and good value for most gardens.
- More storage: link two or three butts with a connector kit.
In summer one butt empties quickly once you water a greenhouse every day, so more storage is rarely wasted.
Diverter kits
A diverter fits into the downpipe and sends rain into the butt through a hose. When the butt is full, the water carries on down the pipe instead of overflowing. Check that the kit fits your downpipe, round or square.
Stands and taps
A stand lifts the butt so a watering can fits under the tap.
A water butt at the greenhouse
Fit gutters to your greenhouse and run the downpipe into a butt next to it. You then have water where you need it.
Keep the water clean
- Always use a lid. It keeps out leaves, light and mosquito larvae, and keeps children safe.
- Clean the butt once a year.
- Water seedlings with fresh tap water and keep stored rainwater for established plants.
Our picks for water butts and diverter kits are below. More kit under grow your own.
