How to Fix a Leaking Gutter Joint

There is nothing quite as annoying, or potentially damaging, as the constant drip, drip, drip of a leaking gutter joint during a heavy Scottish downpour.

While it might seem like a minor nuisance, a leaky joint can allow water to run down your exterior walls, leading to penetrating damp, ruined brickwork, and unsightly stains.

Fortunately, fixing a leaking gutter joint is a relatively straightforward DIY task if you catch it early and have a head for heights. Here is exactly how to stop the drip and secure your roofline.

Why Do Gutter Joints Leak?

Before you start applying fixes, it helps to understand the root cause. Plastic UPVC gutters are connected using “union brackets” which contain rubber gaskets (seals). Over time, these joints fail for a few common reasons:

Degraded Rubber Seals: Weather exposure and fluctuating temperatures cause the rubber gaskets to dry out, shrink, and crack.
Thermal Expansion: Plastic gutters expand in the heat and contract in the cold. This constant movement can pull the joints apart.
Trapped Debris: Grit, moss, and dirt can get wedged between the gutter length and the rubber seal, breaking the watertight bond.

Step-by-Step: How to Fix a Leaking Gutter Joint

If you are comfortable safely using a ladder, here is the process to repair a standard plastic gutter joint.

1. Clean the Gutter Completely

You cannot repair a joint that is covered in sludge. Set up your ladder safely on firm, level ground. Use a scoop to remove all leaves, dirt, and standing water from the guttering around the leaking joint. Use a sponge and some warm soapy water to scrub the inside of the gutter and the joint completely clean, then dry it thoroughly with an old rag. Sealant will not stick to a wet or dirty surface.

2. Squeeze and Release the Joint

To get to the problem area, you need to unclip the guttering from the union bracket. Squeeze the sides of the plastic gutter inwards; this should give you enough flex to unclip it from the bracket.

3. Inspect the Rubber Gasket

Look closely at the rubber seal inside the bracket. If it is simply dirty, wipe it down. If the rubber is brittle, cracked, or flattened, it needs to be replaced. You can buy replacement gaskets at most DIY stores. However, if the plastic bracket itself is cracked, you will need to replace the entire union piece.

4. Apply Gutter Sealant

If the seal is intact but just needs reinforcing, a high-quality, weather-resistant gutter sealant is your best friend.

Load a tube of gutter sealant into a caulking gun.
Apply a generous bead of sealant along the inside of the union bracket, right over the rubber gaskets.
Avoid using standard bathroom silicone, as it will not withstand outdoor UV rays and freezing temperatures.

5. Reassemble and Test

Firmly press the gutter lengths back down into the union bracket until they click securely into place. The pressure should squash the sealant, creating a watertight barrier. Wipe away any excess sealant that squeezes out over the edges. Wait for the sealant to cure (check the manufacturer’s instructions, but usually 24 hours), and then pour a jug of water over the joint to test your repair.

When to Skip the DIY and Call the Experts

While a single leaking joint is an easy weekend fix, patching up an old, sagging gutter system that leaks at every seam is a losing battle. If your gutters are constantly dripping, overflowing, or situated over a tricky conservatory, it’s time to call in the professionals.

At Sam’s Gutter Cleaning, we don’t just scoop out the leaves. If we spot a minor leak while we’re up there, we will repair it for you. We believe in doing the job right the first time, with no hidden fees and no nonsense.

If you want to protect your home from water damage without spending your weekend up a ladder, book our professional gutter cleaning service today. Sam, Martin, and the team will use our high-reach SkyVac systems to get your roofline flowing perfectly again - safely from the ground.