How to replace a gutter downpipe

Video by Wickes. This walk-through is inspired by the Wickes how-to series, which covers a wide range of home maintenance tasks including guttering and drainage. The Wickes channel is a reliable starting point for understanding plastic rainwater systems — the same push-fit principles they demonstrate for guttering apply directly to downpipe replacement.

1. Identify exactly what needs replacing

Before buying anything, have a proper look at the whole downpipe run on a dry day. Cracks often appear at joints first, but the surrounding sections of pipe can also be brittle — especially on older properties where the plastic has been baking in the sun for twenty years. Press gently along the pipe; if it flexes more than it should, replace the whole run rather than just the damaged section.

Note the profile of your existing system: round, square, or rectangular. The most common residential size in the UK is 68 mm round downpipe or 65 mm square. Take a short piece to the builders merchant if you are unsure — mixing profiles from different manufacturers is possible with adapters, but it is far simpler to match like for like.

2. Gather your materials and set up safely

You will need: replacement downpipe in the right length (cut to size on site with a hacksaw), pipe clips, any offset bends needed to bring the pipe back to the wall, and a shoe at the bottom to direct water into the drain. Most push-fit plastic systems need no adhesive — the spigot simply pushes into the socket. That said, some older bonded systems do use solvent cement, so check before you start.

Work from a stable ladder with the feet on firm ground, or use a scaffold tower for a two-storey run. Do not lean a ladder against the guttering itself — it will crack it. Have someone foot the ladder if there is nobody around, a ladder stay hooked over the fascia is worth fitting. Safety first, especially on a slippy day.

3. Remove the old downpipe and clips

Start at the top. The downpipe connects to the gutter outlet via a running outlet or stop-end outlet at the fascia. Twist the top of the pipe anti-clockwise (or simply pull it) to release it from the outlet spigot. Work your way down, unclipping each pipe bracket from the wall as you go. Most brackets are screwed into the masonry with a plug and screw — a cordless drill and a flat pry bar make light work of it.

On older properties you may find cast iron rather than uPVC. Cast iron downpipes are heavy and the fixings corrode, so be careful when levering them off — chunks of mortar often come away with the fixings. Wear gloves; the cut edges of old cast iron are sharp. Dispose of cast iron sections at a local recycling centre rather than in the general skip if possible.

4. Mark and fix the new pipe clips

Hold the top of the new downpipe up to the outlet and mark the wall where the first clip needs to go. Clips should be spaced no more than 1.8 m apart, with one directly below any joint or bend. Use a plumb line or laser level to get them in a straight vertical line — even a slight bow in the pipe will look untidy and may cause water to pool at the joints.

Drill into the masonry with a hammer drill and the correct size bit for your wall plugs. On a rendered wall in a Sandwich terrace, you are usually drilling into soft brick behind the render, so a 6 mm plug and a 4 mm screw is normally adequate. Harder engineering brick needs more care — go slowly and let the drill do the work rather than forcing it.

5. Fit the new pipe sections

Connect the top of the new pipe into the outlet spigot at the gutter. Push-fit systems need a 6 to 10 mm expansion gap between the end of the pipe and the back of the socket it sits in — do not push it fully home or the pipe has nowhere to go when it expands in warm weather. Mark the pipe at the right depth with a felt-tip before you fit it so you get a consistent gap.

Work downward, clipping each section in as you go. Where you need to join two lengths, use a pipe socket connector and a clip directly over the joint. At the bottom, fit a shoe to direct water away from the wall and into the drain gully. If the drain is offset, use a 112° offset bend. These are standard fittings available at any builders merchant or large DIY store.

6. Test the system and check for leaks

Once everything is clipped and connected, run water from a hosepipe into the gutter outlet and watch it travel the full length of the downpipe. Check each joint carefully. Push-fit joints that drip usually just need pushing together a little more firmly, or the spigot may need a smear of silicone grease to seat properly. Do not use jointing compound on push-fit uPVC — it is not needed and can degrade the plastic.

Step back and look at the pipe from a distance. It should sit parallel to the wall with an even gap all the way down. If it bows or kicks out at a joint, loosen the nearest clip and straighten it before retightening. The whole thing should look tidy and run true — a well-fitted downpipe will last twenty years or more without any further attention.

When to call a handyman

Get Richard involved if the downpipe run is on a two-storey or taller wall and you are not comfortable working at height, if the existing fixings have pulled out of the masonry and need re-drilling and plugging, or if the outlet at the gutter itself is cracked and needs replacing at the same time. It is also worth calling if the pipe connects to an underground drain — making sure that connection is sound and not causing a blockage further down the line is worth checking properly.