Why Is My Gutter Leaking at a Joint Even Though It Isn't Blocked?
For rainwater dripping from the connection between two gutter lengths, an angle or outlet even though the gutter channel itself is clear.
What this usually means
A gutter can leak at a joint even when it is completely clear because the problem is often the joint itself, not a blockage. The rubber seal may be perished, dirty, displaced or missing; the gutter ends may have moved out of the union because of thermal expansion; the union clip or bracket may be loose; or a sagging run may be loading the joint and letting water escape. A joint leak is therefore different from a gutter that simply overflows because it cannot carry enough water.
What may be causing this
The rubber joint seal is worn, dirty or displaced
Clues: Water drips directly from the union even with a clear gutter, especially on older uPVC systems.
What to do: The joint normally needs to be opened, cleaned and fitted with a sound compatible seal or replacement union.
The gutter has moved within the union
Clues: One gutter end no longer sits at the fitting’s insertion mark, or a visible gap has opened at the joint.
What to do: Plastic gutter systems need room for thermal movement while still being correctly seated in the fitting. The run may need repositioning and the union secured as designed.
The union clip or support bracket is loose or damaged
Clues: The joint sags, twists or moves when the gutter fills with rainwater.
What to do: Replace the damaged fitting or bracket and restore the correct support around the joint.
The gutter run has sagged or lost its fall
Clues: Water sits beside the joint after rain, the run visibly dips, or the joint leaks more during prolonged rainfall.
What to do: The supporting brackets and gutter alignment need correcting so water flows toward the outlet instead of loading the union.
How to check what is happening
A joint seal or fitting problem is more likely than a blockage or capacity issue.
Support or alignment may be contributing to the leak.
Thermal movement, poor engagement or fitting damage is likely.
The fitting itself needs attention rather than simply more drainage capacity.
Can you fix this yourself?
Diagnosing the leak from ground level is straightforward, but the repair usually requires safe access at eaves height and opening the union fitting. On a low single-storey section with genuinely safe access, a competent homeowner may replace a compatible union seal or fitting; otherwise a roofer or guttering specialist is the safer route.
- Binoculars or phone zoom for ground-level inspection
- Spirit level only if the gutter can be reached safely
- Manufacturer-matched union or seal if replacement is undertaken
What you can safely try
- 1
Confirm that the water is coming through the joint
During rain, check whether water drips from the underside of the union or simply spills over the top. Those are different faults and need different fixes.
- 2
Look for sagging or a pulled-apart joint
From the ground, sight along the gutter and compare the joint height with neighbouring brackets. A dip can keep the union permanently loaded with water.
- 3
Identify the gutter profile and manufacturer if possible
Half-round, square and deep-flow systems use different unions and seals. Replacement parts should match the existing system rather than being forced to fit.
- 4
Renew the fitting or seal rather than smearing the outside
A durable repair normally means opening the joint, cleaning the mating surfaces and replacing a damaged seal or union according to the system instructions.
- 5
Correct the support and fall at the same time
If the joint is sagging or the bracket has failed, replace or reposition the support so the repaired union is not immediately stressed again.
Call a roofer if…
- The gutter cannot be reached without working at unsafe height.
- Access is above a conservatory, extension, fragile roof or sloping ground.
- The fascia or bracket fixing area is rotten or loose.
- Several joints are leaking or the whole run is badly distorted.
- Water is entering the wall or causing an internal damp problem.
Get the right roofer.
We already know this problem maps primarily to a roofer. Choose the closest type of work, add your postcode and continue in the form.
Sources used for this guide
We prefer primary UK guidance, regulators and manufacturers for technical and safety-sensitive claims.
- Rainwater Systems Product BrochureFloPlast
- Evolve Gutter System Installation GuideMarley Alutec
- Guttering Specialist Job ExamplesMyJobQuote
Last reviewed: 31 August 2026. Home Manual updates review dates only when the substance of a guide is checked or changed.