How to make a rainwater barrel?

Making your own rainwater barrel is a satisfying DIY project that creates a functional water conservation system at a fraction of the cost of a commercial product. A homemade barrel can be built for £15 to £40.

Sourcing a Suitable Barrel

The best choice is a food-grade plastic drum that previously held food ingredients like olive oil or fruit juice concentrates. These are typically 200 to 250 litres, made from HDPE, and safe for water storage. Never use drums that held chemicals or industrial fluids. Check online marketplaces like Freecycle or Gumtree, or ask local food manufacturers and restaurants. Look for drums with screw-top lids.

Cleaning and Preparing

Rinse the drum several times, then clean with a solution of dish soap and warm water using a long-handled brush. If the drum held oil, a degreasing agent may be needed. Rinse thoroughly after cleaning. Allow to dry completely before modification. If the top has been cut off, you will need a secure lid.

Installing the Tap

Drill a hole near the bottom of the barrel — about 5 to 10 centimetres from the base — using a hole saw or step drill bit. Insert a bulkhead fitting to create a watertight seal. Apply plumber's tape to threads before tightening. Attach a garden hose tap or ball valve. Test for leaks by filling with a few inches of water.

Installing the Overflow

Drill a second hole near the top, about 5 centimetres below the rim. Fit a bulkhead fitting and hose connector. The overflow should be at least as large as the inlet (20-25 mm diameter) to handle heavy rainfall. Connect a hose to direct water away from foundations. Multiple barrels can be connected in series using overflows as inlets for subsequent barrels.

Adding the Inlet and Screen

Cut a hole in the lid and fit a screened inlet using stainless steel or brass mesh with apertures no larger than 1 mm. The screen keeps leaves, insects, and debris out and prevents mosquito breeding. Alternatively, install a downpipe diverter that connects directly to the barrel. Consider painting the barrel with exterior-grade spray paint to block light and prevent algae growth.

Finishing and Installation

Before installing your barrel, consider painting it to match your garden aesthetic and to block light — light penetration promotes algae growth. Use exterior-grade spray paint designed for plastic, applying several light coats. Earthy colours help the barrel blend into the garden. Position the barrel on a firm, level surface — a purpose-built stand raises it high enough to fill a watering can from the tap and improves water pressure. Connect the downpipe diverter to your downpipe according to the diverter instructions, then connect the diverter hose to the barrel inlet. Test the system by running water into the gutters — check that the diverter directs water into the barrel, that the overflow works correctly, and that the tap does not leak. Your homemade rain barrel is now ready to collect and provide free, soft rainwater for your garden.

Winter Preparation and Year-Round Care

In colder climates, preparing your rain barrel for winter is essential to prevent freeze damage. Before the first hard frost, disconnect the barrel from the downpipe diverter, drain all water completely, and store the barrel upside down or indoors for the winter. Reconnect it in spring when frost risk has passed. If you want year-round operation, consider insulating the barrel with foam wrap or installing a small aquarium heater to prevent freezing. Clean the barrel annually by scrubbing the interior with a mild bleach solution and rinsing thoroughly. Inspect all fittings, seals, and the screen for wear and replace as needed. With proper seasonal care, your homemade rain barrel will provide many years of reliable service, supplying free, soft water for your garden and reducing your environmental impact.