Short answer
Overflowing gutters, water stains on the wall and a weak trickle from the downpipe in heavy rain usually mean a blockage. Gutters block with leaves, moss and silt, and downpipes block where that debris collects at bends and the bottom outlet. Many downpipe blockages can be cleared from the bottom; gutters above a single storey are safest cleared from the ground or by a professional.
Signs of a blocked gutter or downpipe
The clearest sign is water spilling over the front of the gutter during rain instead of running away down the pipe. Other signs include green or dark streaks on the wall below the gutter, moss or small plants growing along the gutter, a sagging section that holds water, damp patches on an inside wall, and water pooling or splashing at the base of the house.
For downpipes, watch what happens in a heavy shower. If water backs up in the gutter, overflows near the top of the pipe or gurgles, but only a trickle comes out at the bottom, the pipe is probably partly blocked. Water leaking from the joints of a downpipe can also point to a blockage further down.
Common causes
Leaves and seeds from nearby trees are the usual culprits, followed by moss and grit washed off the roof. In the downpipe, debris tends to lodge at the swan-neck bends near the top and at the shoe or bend at the bottom. Balls, toys and old nesting material can also get stuck. If there are birds nesting in or near a gutter, leave an active nest undisturbed.
Not every overflow is a blockage. A gutter that has lost its slope towards the outlet, a joint that has come apart, or a gutter that is too small for the roof area can all cause overflowing, even when the gutter is perfectly clear.
How to unblock a downpipe
- Start at the bottom. Clear leaves and silt from the gully, drain or water butt connector that the downpipe feeds into.
- If the pipe ends in a removable shoe or access section, take it off and pull out any debris you can reach.
- Push a garden hose up the pipe from the bottom and turn it on gently to loosen the blockage, standing clear of the water that comes back down.
- For a stubborn blockage, a flexible drain rod pushed up from the bottom can help break it up. Work gently so you do not push joints apart.
- Once water flows freely, check the joints for leaks and refit any parts you removed.
- If the blockage is at the top swan-neck, it may need clearing from the gutter end. Only do this if you can reach it safely, and never climb onto the roof.
How to unblock a gutter
Clearing a blocked gutter means removing the debris, not flushing it into the downpipe. On a single-storey building, that can be done carefully from a ladder; on higher buildings, it is safer from the ground with a pole-mounted tool or a gutter vacuum. Our guide to cleaning gutters covers both methods and the ladder safety steps in detail.
Once clear, run water along the gutter and watch it reach the outlet. If it pools in the middle of a run, the gutter may need its brackets adjusting to restore the fall, which is a repair rather than a clean.
Avoid these mistakes
Do not pour drain-clearing chemicals into gutters or downpipes. They are designed for internal waste pipes, can damage plastic and metal rainwater fittings and end up in the soil or surface water drains.
Do not lean ladders against plastic gutters, stand on extension or conservatory roofs to reach a gutter, or hammer on pipes to dislodge a blockage, which can crack the fittings.
When the problem is below ground
If the downpipe is clear but water still backs up at the bottom, the blockage may be in the underground drain or soakaway it connects to. That is a job for a drainage specialist rather than a gutter cleaner.
To stop blockages coming back, clear gutters at sensible intervals for your home. Our guide to how often gutters should be cleaned explains how to work out the right timing, and our guide to gutter guards looks at whether guards help.
When to call a professional
Call a professional if the blocked section is above the first floor, over a conservatory or extension, or if gutters keep overflowing after you have cleared them. Repeated overflowing at the same spot is worth looking at properly, as it can soak a wall over time.
We clear gutters with a high-reach vacuum and camera, so we can see the gutter is fully clear, and we check downpipes are flowing freely and clear blockages where we can reach them. If you can see where the overflow happens, tell us when you ask for a quote. Faults with the gutter itself, or blockages in underground drains, need a repairer or drainage specialist.
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Gutters cleared with a high-reach vacuum and camera, no ladders on your roof. Family-run by Jason and Lucas Prior, covering south Essex.
Frequently asked questions
Why are my gutters overflowing?
Usually because the gutter or downpipe is blocked with leaves, moss or silt. If the gutter is clear, it may have lost its slope, have a failed joint or be too small for the roof, which needs a repair.
How do I unblock a downpipe from the bottom?
Clear the gully or drain at the base, open any access shoe, then push a hose or flexible drain rod up the pipe to break the blockage, standing clear of the water that runs back down.
Can a blocked gutter cause damp?
It can. Water overflowing onto the same patch of wall each time it rains can soak into the masonry, leading to damp patches inside, staining outside and damage to fascias.
Related guides
- How to clean gutters: clearing gutters by hand or from the ground, with the ladder safety steps that matter most.
- How often should gutters be cleaned?: working out the right gutter-cleaning interval for your home, rather than following a rigid rule.
- Do gutter guards work?: a balanced look at mesh, brush and foam gutter guards, what they do well and where they fall short.
- What affects the cost of gutter cleaning: the factors that change a gutter cleaning quote, what a good quote should include and how to compare quotes like for like.