Michael Hargreaves
Why Fit a Water Butt?
If you garden in Britain, you already know the paradox: it rains for weeks, then the heavens close up just as your tomatoes are setting fruit and your bedding plants are gasping. A water butt solves both halves of that problem. Every square metre of roof can shed roughly 600 litres of water over a typical year, and a modest 200-litre butt will catch a surprising amount of it from a single downpipe. That water is soft, free of the chlorine and limescale that mains supply carries, and — crucially — it comes out of a tap you can carry to the far end of the garden without unreeling a hosepipe.
Add a hosepipe ban or a metered supply into the mix and the sums look even better. Most water companies now charge by the cubic metre, and a butt that fills and empties a dozen times through the summer is money you have not spent. It is also, frankly, one of the most satisfying weekend jobs in the garden: an afternoon's work that keeps giving for years.
Choosing the Right Butt and Position
Butts come in three broad flavours. Traditional oak barrels look wonderful against a brick wall but need a liner and will dry and shrink if left empty. Moulded plastic butts are cheap, light and won't rot, though they can go brittle after a decade of UV. Slimline or wall-mounted designs are the answer where space is tight — a narrow terrace, a side return, or a tiny courtyard where a full circle would block the path.
Size matters more than looks. A 100-litre butt will be brimful after a decent shower and empty again within a week of warm weather. Aim for at least 200 litres, and consider linking two together with a connector kit so the second fills once the first is full. Before you commit, check these points:
- Height: the tap must sit above your watering can, so raise the butt on a purpose-made stand or a few sturdy paving slabs. Every 30cm of height gives you better flow.
- Stability: a full 200-litre butt weighs over 200kg. A level, firm base is not optional.
- Sunlight: keep it out of full sun if you can. Warm, light water grows algae, and a dark or shaded butt stays cleaner.
- Access: leave room to lift the lid, and site it near the beds you water most often.
Connecting to the Downpipe
There are two main methods, and the choice depends on the material of your downpipe. The simplest is a diverter kit, which replaces a short section of pipe with a fitting that sends water sideways into the butt through a flexible hose. When the butt is full, the diverter automatically sends the rest down the drain, so you can never overwhelm it.
For plastic downpipes — the square or round uPVC that most modern houses have — you can cut a section out with a fine-toothed saw or a junior hacksaw. Measure twice, cut once, and leave a clean square edge. Slot in the diverter, tighten the jubilee clips or the supplied collars, and check the fall is gentle towards the butt. If you have cast iron or a downpipe you would rather not cut, a rain saucer or downpipe rainwater collector sits on top and simply catches what spills over the top — cheaper, less efficient, but completely reversible if you rent.
A word of caution: never intercept a downpipe that carries wastewater, and if your drains serve a combined system, check your local rules before diverting significant volumes. A diverter that returns surplus to the drain keeps everything compliant and safe.
Keeping the Water Clean and the Butt Healthy
Rainwater straight off a roof carries dust, moss and bits of grit, so a little housekeeping goes a long way. Fit a leaf catcher or gutter guard to the downpipe, or simply clean your gutters before the autumn rains arrive. Inside the butt, a filter basket under the inlet keeps debris out, and a fine mesh lid stops insects breeding in still water.
Once a year, in late winter when the butt is nearly empty, tip it, rinse it out with a stiff brush and a little diluted vinegar, and clear any sludge from the bottom. Do not use bleach or detergent — traces will harm your plants. If you plan to store water for long periods, drop in a purpose-made water butt treatment or a small handful of barley straw to keep algae in check.
- Water early in the morning or late in the evening, so less is lost to evaporation.
- Water the soil, not the leaves — rainwater is best delivered to the roots.
- Use a can with a rose for seedlings and a bare spout for established plants.
- Top up the butt from the mains only in a genuine drought; otherwise let the rain do it.
Putting It to Work in the Garden
Rainwater is slightly acidic and free of the salts that build up in tap water, which makes it the first choice for ericaceous plants like blueberries, camellias and rhododendrons. It is also ideal for tomatoes, courgettes, cucumbers and anything in a container, where limescale quickly spoils compost. Fill your watering can from the butt rather than the kitchen tap and you will notice the difference in leaf colour within a season.
Don't overlook the wider garden. A full butt is a handy dip for rinsing muddy tools, sluicing the patio, or topping up the bird bath. It takes the edge off a hot day for a new hedge and can be run through a simple drip line for a raised bed if you fit a small submersible pump. For most of us, though, a can and a bit of elbow grease is all that is needed — and there is something quietly pleasing about watering your beans with the very rain that fell on your roof last Tuesday.
