How to fix a leaking gutter joint

Inspired by a helpful YouTube guide. This walkthrough draws on the OSMA Rainwater tutorial "How to fix a leaking gutter joint", produced by Wavin’s OSMA rainwater team — the manufacturers of one of the most widely-fitted plastic gutter systems in the UK. The video is concise and practical, showing clearly how a dislodged or worn gasket causes most joint leaks and how simply replacing it sorts the problem.

1. Work safely at height

Set your ladder on firm, level ground and tie it off at the top if possible. Never lean a ladder directly against the gutter — it can crack plastic sections and will shift under your weight. Use a standoff bracket to keep the ladder away from the gutter run.

Do not overreach. It is always quicker to come down and move the ladder than to treat a fall. If the gutter is on a two-storey gable or a difficult angle, this is a job for a professional with the right access equipment.

2. Identify the leaking joint

Watch the gutter during rain to see exactly where the water is escaping. Alternatively, run a hose into the top of the run and watch from below. A leaking joint usually shows water dripping straight down from the union connector or a union bracket — the plastic clips that join two gutter sections together.

Sometimes the joint itself looks fine on a dry day. The gasket — the rubber seal inside the connector — may be dislodged, perished, or missing altogether.

3. Disconnect the joint

Most plastic gutters use a simple push-in connector held by clip tabs. Squeeze or lever the tabs to release the gutter section from the union. You may need to unclip the gutter from the fascia brackets either side to get enough slack to pull the sections apart.

Have a cloth ready — there will be standing water in the gutter that goes somewhere when you move sections around.

4. Clean both gutter sections thoroughly

Wipe the inside ends of both gutter sections and the inside of the union connector with a dry cloth. Remove any grit, moss, or old sealant. The rubber gasket needs to seal against clean plastic — any debris between them and the joint will leak again immediately.

Check the end of the gutter section for cracks. A hairline crack running into the gutter from the end can look like a joint leak but will not be fixed by replacing the gasket.

5. Check or replace the gasket

Look inside the union connector for the rubber gasket. It should sit evenly in the channel around the inner face of the connector. If it is twisted, folded over, or has slipped to one side, reseat it carefully with a flat screwdriver.

If the gasket is perished, cracked, or missing, take the connector to a builders’ merchant and match it. Most replacement gaskets cost just a few pence. That said, if the connector itself is cracked or brittle, replace the whole union while you are up there — it is the same clip-in fit.

6. Reassemble and test the repair

Push the gutter section back into the union, making sure the end seats fully behind the gasket and clips home with an audible click. Refit the gutter to the fascia brackets. Pour water in at the top of the run and check for leaks at the repaired joint while it is flowing.

If it still drips, disconnect again and check the gasket is properly seated. A small amount of gutter sealant applied to the inside of the joint can help if the gasket is a marginal fit — but on most UK plastic systems, correct reassembly with a sound gasket is all that is needed.

7. Check the rest of the run while you are up there

It is worth running your eye along the whole gutter while the ladder is up. Check the fall — water should run freely toward the downpipe without pooling. Sagging sections cause moss and debris build-up that can lead to more joint leaks over time.

Clear any leaves or grit from the gutter and check the downpipe is flowing freely. A blocked downpipe can cause overflow at a joint that is otherwise perfectly sound.

When to call a handyman

Call Richard if the gutter is cracked or brittle and needs a section replacing, if the fascia board behind it feels soft or rotten, if the job is on a difficult two-storey elevation, or if the downpipe is blocked at ground level and needs rodding out. A gutter repair that is done once and done properly is far better value than patching a run that has been ignored for years.