Water sources
Your roof is a reservoir you already own.
Rainwater collected from a roof is unmetered, unrestricted and better for plants than treated mains water. Most UK households let tens of thousands of litres a year run straight into the drain.
Roof yield calculator
What you'd collect
Per year
21,760litres
- Typical summer month
- 1,088 litres
- Suggested storage
- 9 × 210L butts
Figures assume roughly 85% capture after splash, overflow and gutter losses. Linking butts together is far cheaper than buying one large tank.
Can you run a dripline off a water butt?
Not reliably on gravity alone. A butt gives you well under 0.1 bar of pressure, and inline dripline emitters are designed for mains pressure. Gravity feed works for short runs of open-ended soaker hose on level ground, but it will not water a whole garden evenly.
The practical setup is a small pressure pump on the butt outlet, or — far simpler — a mains-fed dripline for the beds and butt water saved for pots, seedlings and topping up. Because a dripline uses a fraction of the water a hose does, the mains cost stays tiny.
Getting more from what you collect
- Fit a diverter to a downpipe rather than a standalone butt — you catch far more.
- Raise the butt on a stand so a watering can fits under the tap.
- Keep it lidded: light grows algae, and open butts are a drowning risk for wildlife and children.
- Link two or three butts with a connector kit so overflow fills the next one instead of the drain.
- Empty stored water onto beds before heavy forecast rain so you have capacity to catch it.
- Rainwater is slightly acidic — ideal for blueberries, rhododendrons and camellias that dislike tap water.