Why a water butt earns its place

On a smallholding, dry spells have a way of arriving just as the runner beans are flowering and the courgettes are swelling. Mains water is treated, cold, and metered, and a hosepipe ban can turn a kitchen garden from productive to parched in a fortnight. A rain barrel — or water butt, as most of us call it — is one of the simplest traditional country skills you can revive. It catches free soft water from your roof, stores it close to the beds, and gives you a supply you can dip into without a guilty glance at the meter.

One 200-litre butt will not irrigate an acre, but it will keep a dozen raised beds, a fruit cage, and a greenhouse border ticking over through a dry week. Two butts linked together are better still. The water is lukewarm rather than icy, which suits tomatoes, cucumbers, and young seedlings far better than a blast from the cold tap. And because it is soft, it will not leave the white crust on pots and seed trays that hard water does.

Choosing the right spot and setting a firm base

Position beats size every time. Put the butt under a downpipe that serves a decent roof area, ideally the one nearest your kitchen garden. A shed or outbuilding roof of 20 square metres will fill a 200-litre butt in a modest shower, so you do not need a huge house roof to make this worthwhile.

• Keep it close to the beds. Every metre of hosepipe costs you pressure, and you will use the butt far more if it is a few steps from the salad leaves.
• Choose a shaded spot. Full sun encourages algae and warms the water. A north-facing wall or the shady side of a shed is ideal.
• Build a level, solid base. A full butt weighs over 200kg. Use paving slabs, sleepers, or concrete blocks, not bare soil.
• Raise it 30–45cm. A stand or a stack of blocks gives you better gravity flow and makes the tap easier to reach with a watering can.

Check the fall on the gutter and make sure the downpipe is sound. If the gutter is choked with moss and leaves, clear it first — otherwise the first heavy rain will send a brown slurry into your butt.

Fitting a diverter to your downpipe

A diverter is the clever bit. Instead of cutting the downpipe and letting water splash into an open butt, you fit a unit that sends rainwater into the barrel until it is full, then lets the rest carry on down the drain. Most UK downpipes are either 68mm round or 65mm square, so measure before you buy.

• Mark the downpipe at the height of the butt’s inlet, allowing for the base and stand.
• Remove a section of downpipe with a hacksaw, leaving clean square ends. File off any burrs.
• Fit the diverter according to its instructions, usually with a rubber seal and clips. A bead of silicone helps on awkward joints.
• Connect the flexible hose to the butt inlet. Fit the overflow pipe and lead it to a drain, soakaway, or a second butt.

Take your time with the overflow. If it dumps water against the wall, you will soon have a damp patch and a grumpy builder. A length of 40mm waste pipe running to a flower border or gravel soakaway is usually enough.

Taps, hoses and getting water to the beds

Fit a brass tap about 10–15cm above the base of the butt, using PTFE tape on the threads. That low position lets you use almost every drop. Gravity gives roughly 0.1 bar per metre of head, so a butt raised 1 metre offers about 0.1 bar — enough for a short hosepipe and a watering wand, but not for a sprinkler or a long soaker hose.

Work with that limitation rather than against it. Use a short, wide-bore hose. Fill a watering can directly from the tap for delicate seedlings. For beds, run a hose to a wand and water the soil, not the leaves, early in the morning or in the evening. A good mulch of compost or straw will cut evaporation and halve the number of trips you make. If you want to run drip lines, a small submersible pump and a timer will turn the butt into a proper irrigation reservoir, but that is a project for another weekend.

Keeping the water clean and the butt working

Rainwater from a roof carries bird droppings, moss, and grit. That is fine for ornamentals, fruit bushes, and established vegetables, but it is not drinking water. A few sensible habits keep it sweet.

• Fit a tight lid and a fine mesh over the inlet to keep out leaves and mosquitoes.
• Use a gutter guard or leaf trap on the downpipe, and clean your gutters each autumn.
• Empty and scrub the butt once a year with plain water and a stiff brush. Never use detergent.
• Water the soil around salad crops rather than splashing the leaves, and wash harvested produce as usual.

If algae still forms, move the butt further into the shade or wrap the sunny side with a piece of old sacking. A handful of barley straw in a mesh bag can help keep the water clear, an old pond-keeper’s trick that costs almost nothing.

Through the seasons: winter care and summer routines

In winter, a full butt is a frozen butt waiting to crack. Before the first hard frost, drain it down, leave the tap open, and disconnect the diverter hose so ice has somewhere to expand. If your butt is frost-proof, you can leave some water in, but check the manufacturer’s advice. Come spring, reconnect everything, give the inside a rinse, and let the April showers do the filling.

Through summer, make a habit of checking the level after every dry week. Use the butt first for the thirstiest crops — courgettes, beans, tomatoes, and soft fruit — and save mains water for emergencies. A simple dipstick, or just a tap that runs dry, will tell you when to switch. Link a second butt to the overflow if you have space, and you will sail through most dry spells without ever unrolling a hosepipe from the tap. It is a small piece of old-fashioned husbandry, but it pays you back every rainless week.