Why Rainwater Beats the Mains Tap

Rainwater is the garden's natural tipple. It is soft, free of the chlorine and fluoride added to mains supplies, and slightly acidic — ideal for ericaceous plants such as rhododendrons, camellias, and blueberries. Unlike tap water, it does not leave a chalky film on leaves or gradually raise the pH of your soil. Collecting it also eases pressure on reservoirs during dry spells, and it keeps your watering can full when hosepipe bans are in force. A modest 200-litre butt can fill around twenty standard watering cans, which is often enough to carry a small garden through a fortnight of hot weather. For pots and containers, rainwater is especially valuable because repeated tap watering can lead to a build-up of salts in the compost.

Choosing and Siting a Water Butt

Water butts come in many shapes and sizes. A 100–200 litre butt suits a small garden or a few pots; 300 litres or more is better for a larger plot with generous borders. Slimline designs fit narrow gaps beside a shed or wall. Place your butt on firm, level ground — paving slabs or a concrete base — not bare soil, which shifts and settles. A sturdy stand raises the tap, giving better gravity flow into a watering can. Site it near a downpipe that receives rain from a decent roof area. If you have room, link two butts with a connector kit so the second fills once the first is full. Keep the butt out of full sun to reduce algae and evaporation; a dark-coloured butt or a shade cover helps here.

Fitting a Downpipe Diverter

Diverting a downpipe is straightforward with a kit. You cut a section of downpipe, fit the diverter, and run a short hose to the butt. Position the diverter at least 30 cm above the top of the butt so water flows freely. Most kits include a filter to keep leaves and grit out. The diverter also acts as an overflow: when the butt is full, water continues down the drain. Check local regulations — in most UK homes this is permitted, but you should not alter shared drainage without advice. Never drink the collected water, and avoid using it on edible crops grown in soil where roof runoff may contain contaminants. If your roof is old or painted, consider using the water only on ornamental plants.

Watering Pots and Borders Wisely

Use a watering can or, for larger borders, a soaker hose connected to the butt's tap. Gravity gives low pressure, so keep runs short — no more than 10–15 metres. Water at the base of plants, not over the leaves, to reduce fungal disease. Early morning or late evening reduces evaporation. Prioritise containers, hanging baskets, newly planted shrubs, and vegetables. Established borders can often wait longer if you have mulched well. A simple dip test — push a finger into the soil — tells you whether water is needed. Deep, occasional watering encourages roots to go down, making plants more drought-tolerant. Avoid little and often sprinklings, which encourage shallow rooting.

Keeping the System Healthy

Maintenance is minimal but matters. Clean gutters each autumn to stop debris entering the butt. Fit a lid or fine mesh to keep out leaves, mosquitoes, and midges. Empty and scrub the butt once a year, ideally in late winter, and check the diverter for blockages. In very cold spells, a full butt can crack; leave some air space and insulate exposed pipework, or drain it if severe frost is forecast. Algae is harmless but unsightly — a dark butt or shade cover helps. If you see wriggling larvae, a few drops of cooking oil on the surface can break the breeding cycle. Also check that the overflow runs away from your house foundations.

Getting the Most from Every Drop

Small changes stretch your supply. Group pots together so they shade each other. Mulch borders with bark or compost to lock in moisture. Install a first-flush diverter to discard the dirtiest initial runoff. Use rainwater for acid-loving plants and for rinsing delicate foliage. If you have a greenhouse, run a pipe from the butt to a drip line. And if you fill your butt quickly, add a second one — linked butts are the cheapest way to double capacity. With a little planning, your garden can thrive on the sky's own supply, whatever the weather brings.