A leaking gutter is one of the most common rainwater problems in the UK. Left unfixed, even a small drip can cause serious damage to fascia boards, brickwork, foundations, and interior walls. The good news is that most gutter leaks can be diagnosed and repaired quickly without replacing the entire system. This guide covers every type of gutter leak, what causes it, and how to fix it.
How to Find Where Your Gutter Is Leaking
Before you can fix a leak you need to find it. The easiest way is to wait for heavy rain and watch the gutter from the ground. Look for water dripping from joints, overflowing from the front edge, or running down the wall behind the downpipe. If you cannot wait for rain, use a garden hose to run water into the gutter from the highest point while someone watches from below.
Common leak locations include the joints between gutter lengths (the most common source of leaks), the joint between the gutter and the running outlet, stop ends at each end of the run, angles where the gutter turns a corner, the connection between the gutter outlet and the downpipe swan neck, and cracks or holes in the gutter itself.
Leaking Gutter Joints — The Most Common Problem
The joint between two lengths of gutter is the single most common place for a leak. On PVC guttering, each joint has a rubber seal inside the union bracket that creates a watertight connection. Over time these seals can perish, shrink, or become displaced, allowing water to drip through.
How to fix a leaking PVC gutter joint:
Start by cleaning the area around the joint thoroughly. Remove any dirt, moss, or debris from inside the gutter and around the seal. Next, unclip the gutter from the union bracket on the leaking side by pushing up on the front edge and lifting the gutter out of the clip. Inspect the rubber seal inside the union bracket. If the seal is cracked, hardened, or misshapen, replace it with a new seal. New seals are available for all major brands including FloPlast, Osma, and Marshall Tufflex.
Before reclipping the gutter, apply silicone lubricant spray to the new seal. This helps the gutter slide into position and ensures a proper watertight fit. Push the gutter back into the union bracket until it sits against the expansion line marked inside the fitting. Do not push the gutter tight against the internal stop — leave room for thermal expansion.
If the seal looks fine but the joint still leaks, the gutter may have moved beyond the seal due to thermal expansion. In hot weather PVC expands up to 3mm per metre. If the gutter was originally pushed too tight, summer expansion can push it past the seal. Reset the gutter to the correct expansion mark and reclip.
Sealing a Gutter Joint That Will Not Stop Leaking
If you have replaced the seal and reset the gutter but the joint still leaks, apply gutter sealant as a secondary fix. Use a gutter-specific sealant (not general purpose silicone) designed for use on PVC rainwater systems. Clean and dry the joint area thoroughly. Apply a bead of sealant along the inside of the joint where the two gutter sections meet. Smooth the sealant with a wet finger to create a neat finish. Allow to cure for 24 hours before exposing to water.
Gutter sealant is a repair solution, not a permanent replacement for a functioning seal. If the joint continues to leak after sealing, the union bracket itself may be damaged or distorted and should be replaced.
Leaking Stop Ends
Stop ends seal the open ends of each gutter run. A leaking stop end usually means the seal has failed or the stop end has become dislodged. To fix it, unclip the stop end from the gutter, clean both surfaces, check the seal, and reclip with silicone lubricant. If the stop end is cracked or distorted, replace it. Stop ends are inexpensive and available for all PVC gutter profiles. Remember that ogee guttering stop ends are handed (left and right) so order the correct one.
Leaking Gutter Angles
Internal and external angles are another common leak point. The fix is the same as for joints — check the seal, clean the surfaces, apply lubricant, and reclip. If the angle piece is cracked or the seal groove is damaged, replace the entire angle fitting. Always fit a fascia bracket within 150mm of each side of an angle to prevent movement.
Leaking Running Outlet
The running outlet is where water exits the gutter into the downpipe. A leak here can drip directly onto the wall below, causing damp. Check the seal between the gutter and the outlet, and the connection between the outlet and the swan neck below. If the outlet itself is cracked, it must be replaced. Running outlets are screwed to the fascia board so replacement involves unscrewing the old one, cleaning the fascia, and screwing the new outlet into position before reclipping the gutter.
Cracked or Damaged Gutter Sections
If the gutter itself is cracked, split, or has a hole, you have two options depending on the severity.
Small cracks or pinholes: Clean the damaged area thoroughly and dry completely. Apply gutter repair tape or a PVC gutter sealant patch over the crack on the inside of the gutter. This is a temporary fix that may last 1 to 3 years.
Large cracks, splits, or holes: Replace the damaged section. Cut out the broken length and fit a new piece using union brackets at each end. Replacement gutter is available in 2m and 4m lengths from FloPlast, Osma, and Marshall Tufflex. Make sure you match the exact brand and profile — different brands are not compatible without a gutter adaptor.
Overflowing Gutters
If water pours over the front edge of the gutter during heavy rain, the gutter is not technically leaking — it is overflowing. This is a capacity or blockage issue rather than a seal failure.
Blocked gutter: The most common cause of overflow. Leaves, moss, and debris build up in the gutter channel and restrict water flow. Clear the blockage by hand or with a gutter scoop, then flush the gutter with a hose. Consider fitting gutter guards to prevent future blockages.
Blocked downpipe: If the gutter is clear but still overflows, the blockage may be in the downpipe or swan neck below. Disconnect the downpipe from the outlet and flush with a hose. Use drain rods or a plumber's snake for stubborn blockages. See our guide on what size guttering you need if overflow is a recurring problem.
Insufficient fall: If the gutter has no slope towards the outlet, water pools in the middle instead of flowing to the downpipe. The recommended fall is 3mm per metre. Check with a spirit level and adjust bracket positions if needed. See our PVC guttering installation guide for how to set the correct fall.
Gutter too small for the roof area: If the gutter is the correct fall, clear of blockages, and still overflows in heavy rain, the profile may not have enough capacity for your roof area. Consider upgrading to a deepflow profile or adding a second downpipe to the run. See our guide on what size guttering you need.
Sagging Gutters
If the gutter sags or dips between brackets, water will pool at the low point instead of flowing to the outlet. Pooling water adds weight which makes the sag worse over time, eventually causing overflows or bracket failure.
Cause: Brackets too far apart, a broken bracket, or a fascia board that has softened. Check that brackets are spaced at the recommended intervals — 600mm maximum for half round and square line, 500mm for deepflow and ogee.
Fix: Add additional brackets at the sag point. If the fascia board is rotten or soft, replace the fascia before refitting the bracket. A bracket screwed into rotten wood will pull out under the weight of water.
Dripping Downpipes
Water dripping from a downpipe joint usually means the connection between two pipe lengths has come apart or the seal has failed. PVC downpipe joints are push fit — check the pipe has not slipped out of the connector. Push it back in and ensure the pipe clip above the joint is tight. If the joint is worn, replace the connector.
If water is running down the outside of the downpipe rather than dripping from a joint, the leak is likely at the swan neck connection at the top. Check the offset bends are fully connected and the gutter outlet is not cracked.
Fixing Leaking Cast Iron Gutters
Cast iron guttering uses bolted joints sealed with putty rather than rubber seals. Over decades the putty dries out and cracks, allowing water to seep through.
To repair a cast iron gutter joint: Unbolt the joint (the bolts may be heavily corroded — use penetrating oil and a hacksaw if needed). Scrape out all the old putty from both faces. Apply fresh linseed oil putty or a modern gutter sealant to both faces. Rebolt the joint using new galvanised bolts. Wipe away excess putty and allow to cure.
If the cast iron gutter is cracked, it can sometimes be repaired with an epoxy metal repair compound. However if multiple sections are damaged, consider replacing with cast aluminium (Alumasc Heritage) which never rusts, never needs painting, and carries a 40 year guarantee. Adaptors are available to connect new cast aluminium to remaining cast iron sections.
Fixing Leaking Aluminium Gutters
Aluminium guttering joints are typically sealed with sealant or bolted with gaskets. If a joint leaks, remove the old sealant, clean both surfaces with a degreaser, and apply fresh gutter sealant. For Marley Alutec Evolve systems with snap fit joints, check the clip has not disengaged and reclip.
When to Repair vs When to Replace
Repair if: The leak is at one or two joints only. The gutter material is in good condition overall. The brackets and fascia are solid. The gutter is less than 15 years old (PVC) or the cast iron is structurally sound.
Replace if: Multiple joints are leaking across the run. The gutter material is cracked, brittle, or discoloured (PVC). The cast iron is heavily corroded with rust holes. The brackets are pulling away from the fascia. The fascia board underneath is rotten. The gutter profile is too small for your roof area (recurring overflows). The cost of multiple repairs approaches the cost of a new system.
If you do replace, see our PVC guttering installation guide for step by step instructions, or browse our full range of PVC, cast iron, aluminium, steel, and copper guttering systems.
Tools You Will Need for Gutter Repairs
Most gutter repairs require only basic tools: a ladder (with stabiliser bar), screwdriver, silicone lubricant spray, gutter sealant, replacement seals, cleaning cloths, a bucket for debris, and gloves. For cast iron repairs add penetrating oil, a hacksaw, spanners, new bolts, and linseed oil putty.
How to Prevent Future Gutter Leaks
Clean gutters twice a year — once in late autumn after the leaves have fallen and once in spring. Remove all debris from the gutter channel, flush with a hose, and check all joints while you are up there.
Check brackets annually — ensure all brackets are tight and the gutter has not sagged. Tighten or replace any loose brackets.
Inspect seals — when cleaning, press each joint gently. If it moves, the seal may need attention before it starts leaking.
Trim overhanging trees — branches dropping leaves into gutters are the number one cause of blockages which lead to overflows and increased stress on joints.
Paint cast iron regularly — if you have cast iron guttering, repaint every 3 to 5 years to prevent rust. Rust weakens joints and eventually eats through the iron.
Check after storms — heavy winds can dislodge gutter sections, shift stop ends, and crack brackets. A quick visual check after any major storm can catch problems before they cause water damage.
Leaking Gutter Repair FAQ
Can I fix a leaking gutter without getting on a ladder? Unfortunately no. Gutter repairs require hands-on access to the joints and fittings. Use a ladder with a stabiliser bar and always have someone holding the base. For two storey properties, scaffolding is the safer option.
What sealant should I use for gutters? Use a sealant specifically designed for guttering and rainwater systems, not general purpose bathroom or kitchen silicone. Gutter sealants are formulated to remain flexible in outdoor temperature ranges and bond to PVC or metal surfaces.
My gutter only leaks in heavy rain — is that normal? No. A properly fitted gutter with functioning seals should not leak in any rainfall. If it only leaks in heavy rain, the joint seal may be partially failed (enough to hold light rain but not heavy), or the gutter may be overflowing due to insufficient capacity or a partial blockage.
Can I use tape to fix a leaking gutter? Gutter repair tape can provide a temporary fix for small cracks or pinholes. It is not a permanent solution and should not be used on joints. Replace the damaged section or fitting as soon as practical.
How much does it cost to fix a leaking gutter? A replacement seal costs under £2. A union bracket costs £3 to £5. A 4m length of replacement gutter costs £8 to £15 depending on the profile. Most gutter leak repairs can be done for under £20 in parts if you do it yourself. A professional roofer or guttering installer will typically charge £50 to £150 to repair a leaking joint depending on access.
Will a leaking gutter cause damp? Yes. Water dripping from a leaking gutter onto the wall below will gradually penetrate the brickwork, causing damp patches on interior walls, peeling paint, black mould, and eventually structural damage. Fix gutter leaks promptly.
My guttering is leaking everywhere — should I replace the whole system? If multiple joints are leaking, the seals have likely perished across the entire run. At this point it is more cost effective and reliable to replace the complete system rather than repairing each joint individually. Browse our PVC guttering range for a complete replacement system.
Can I mix brands when replacing a section? No. FloPlast, Osma, and Marshall Tufflex are not interchangeable. Match the exact brand and profile. If you cannot identify the brand, call us on 03330 151860 with a photo and we will identify it for you. If you must connect two different brands, use a gutter adaptor.
Need Parts for Your Repair?
At Gutters.co.uk we stock every seal, bracket, union, stop end, outlet, and gutter length you need to fix a leaking gutter. All major brands including FloPlast, Osma, Marshall Tufflex, Brett Martin Cascade, Alumasc Heritage, and Lindab. Fast UK delivery. Call us on 03330 151860 if you need help identifying the right parts.