Why a Water Butt Earns Its Place

Anyone who has stood outside in a July heatwave with a watering can and a sad-looking hydrangea knows the value of stored rainwater. A decent summer downpour can fill a 200-litre butt in a single afternoon, and that free water sits there waiting until the dry spell arrives. Rainwater is also better for plants than tap water — it is soft, slightly acidic and free of the chlorine and fluoride that can build up in pots and containers over time.

If you are on a water meter, the saving adds up quietly across a season. If you are not, you will still appreciate the convenience of not trailing a hosepipe across the lawn. And when a hosepipe ban comes in, a water butt is the one thing in the garden that keeps going.

Choosing and Siting Your Butt

For a small garden, a slimline butt of 100 to 150 litres is usually plenty, and many will tuck neatly against a wall or behind a shed. If you have more room, a 200 to 250 litre model gives you a genuine buffer. Consider linking two butts together with a connector kit — the second fills once the first overflows, doubling capacity without taking up much extra footprint.

Site it where the downpipe already falls, ideally close to the beds you water most. A few things to check before you buy:

• Level ground. A full butt is heavy. Pick a firm, flat spot with plenty of shade to slow algae growth.
• A solid base. Two paving slabs bedded on compacted sand is ideal. Soil alone will settle unevenly.
• Room to reach the tap. You will want a watering can or small hose to sit comfortably underneath it.
• A nearby overflow route. Point the overflow towards a border or soakaway, not your neighbour's patio.

Fitting a Diverter to the Downpipe

The diverter is the clever bit. Rather than cutting the downpipe outright and letting everything flood into the butt, a diverter sits in the pipe and sends water into your butt once the flow is steady — and lets it bypass to the drain when the butt is full.

Most UK kits suit standard 68mm round or 65mm square downpipes, so measure yours before ordering. To fit one:

• Position the diverter at least 30cm below the gutter, so splash and debris settle before the water reaches it.
• Mark the hole using the template supplied, then drill with the recommended hole saw — usually 25 to 30mm.
• Clip the diverter body onto the pipe, fit the rubber seal and push the spout home until it clicks.
• Run the short length of hose from the diverter spout into the butt's inlet, with a gentle downward fall.
• Fit the overflow kit at the top, pointing away from the house.

Check the seal with a watering can before the next rain arrives. A smear of silicone around the collar solves most drips.

Raising the Butt for Easy Watering

A butt sitting flat on the ground is useless for filling a watering can. Raise it on a sturdy stand — 30 to 45cm is the sweet spot, giving enough clearance for a can while keeping the whole thing stable. Purpose-made stands are the safest option, but a stack of engineering bricks or a couple of concrete blocks on a paved base works well too.

Remember that water weighs roughly 1kg per litre. A full 200-litre butt plus its stand is well over 200kg, so never balance it on loose soil or a plastic pallet that will flex.

Raising the butt also gives you a little gravity pressure: every metre of height adds about 0.1 bar, so a half-metre lift will push a trickle through a short hose to a soaker line. It will not run a sprinkler, but for a drip line along the tomatoes it is surprisingly effective.

Using Stored Rain Through Dry Spells

Rainwater is best delivered slowly and at the roots. Aim for roughly 10 to 15 litres per week for a mature shrub in warm weather, and more for anything in a container — pots can dry out in a day.

• Water in the early morning or evening to cut evaporation losses.
• Use a can with a fine rose for seedlings and young plants, and a direct pour for established shrubs.
• Mulch after watering with bark or compost to lock the moisture in for days longer.
• Group thirsty pots together so one trip with the can covers more ground.
• Skip rainwater on edibles if your roof has lead flashing or old bituminous felt — use mains water there instead.

Keeping It Working Year-Round

Give the butt a proper clean each spring. Drain it, scoop out any leaf litter, and rinse the inside with a dilute vinegar solution rather than harsh chemicals. Keep the lid firmly on to stop algae and prevent mosquitoes breeding.

Fit a leaf filter or gutter guard upstream, and clear the gutter each autumn so the diverter does not clog. In hard frost, leave the tap slightly open or drain the butt down to a third so expanding ice has somewhere to go. Do that and a well-installed water butt will quietly earn its keep for a decade or more — one rainstorm at a time.