Clogged Downpipe: Causes and Clearing
A downpipe has one job: carry water from the gutter to the ground or drain. When it clogs, the gutter above has nowhere to empty, so it overflows, often down the wall. Because the pipe is enclosed, the blockage itself is usually invisible.
Signs of a clogged downpipe
Water spilling over the gutter near the top of the pipe during rain is the most common sign. Others include a trickle instead of a flow at the bottom, gurgling, a damp stripe down the wall beside the pipe, or a gutter that holds water long after rain has stopped.
What usually causes it
Leaves, moss from the roof, silt and roof granules wash into the outlet and collect at bends. Tennis balls, nesting material and plant growth can also lodge in the pipe. Swan-neck bends at the top, where the pipe kinks back towards the wall, are a classic trouble spot.
Where the blockage tends to be
Most blockages are near the top, at the gutter outlet or the first bend, or at the bottom where the pipe meets a shoe or drain. Long straight runs usually stay clear because water drops through them quickly.
How it is cleared
We clear the gutter first so more debris does not follow, then work from the outlet down, removing material from the swan neck and testing the flow with water. If the blockage is lower, it can be cleared from the bottom. We avoid hammering or forcing rods that could split plastic pipe or crack joints.
After clearing
Once water runs freely, the pipe joints are checked for leaks, because a blockage that has backed up can push water out of the joints. Brackets holding the pipe to the wall are checked too.
Preventing repeat blockages
Regular gutter cleaning is the best prevention, because most of what blocks a downpipe comes from the gutter. Outlet guards can help on some properties but need checking themselves. Treating roof moss reduces how much reaches the gutters in the first place.
Hopper heads and branches
Some older houses have hopper heads, the open boxes at the top of a downpipe that collect water from one or more gutters. They fill with leaves and moss and overflow in heavy rain. Branch fittings, where two pipes join, are also common blockage points because debris catches where the flows meet.
What a blockage does in winter
Water trapped above a blockage can freeze. In plastic pipes the expansion can split the pipe or push sections apart. In cast iron it can crack the pipe. A blocked downpipe going into winter is a repair waiting to happen, so autumn is a good time to make sure pipes run clear.
Downpipes behind conservatories and extensions
Pipes that run behind or through conservatory roofs and extensions are easy to forget and hard to reach. When they block, water often spills onto glass roofs or into corners where it soaks the wall. Mention any hidden or awkward pipes when you ask for a quote.
Downpipe guards and balloons
Wire balloon guards push into gutter outlets to stop leaves entering the pipe. They help on some roofs, but they also catch moss and leaves on top, which can block the outlet entirely. If you have them, they need checking whenever the gutter is cleared.
Downpipes on flat roofs
Flat roofs often drain into a single outlet and downpipe. If that outlet blocks, water ponds on the roof rather than spilling over, which can lead to leaks. Keeping flat roof outlets clear is especially important.
Check after storms
After heavy storms, watch downpipes during the next rain. Debris washed off the roof often lodges at the top bend.
Book downpipe clearing
Our downpipe unblocking service covers this job. Send a photo or describe the problem for a free quote across Hampshire, Surrey and Sussex.
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Frequently asked questions
How do I know if my downpipe is blocked?
Watch during rain. Overflow near the top of the pipe or a weak flow at the bottom are the usual signs.
What blocks downpipes?
Mostly leaves, moss, silt and roof granules washed in from the gutter.
Can I clear a downpipe myself?
Ground-level blockages sometimes can be. Anything at gutter height means working on a ladder, which is the main risk.
Do you clear the gutter too?
Yes, the gutter is cleared first so debris does not follow straight back into the pipe.
Will clearing fix a leaking joint?
Not always. We check joints after clearing and will tell you if one needs repair.
Can a downpipe block in summer?
Yes. Moss dries and rolls off roofs in hot spells, and the first heavy summer storm can wash it into the pipe.
Why does my downpipe gurgle?
Air trapped behind a partial blockage can make it gurgle as water forces past.
Should downpipes have guards?
Outlet guards help on some roofs but need checking, as they can block on top.
Pristine Roof Cleaning Solutions is based in Petersfield, covers Hampshire · Surrey · Sussex and is fully insured to £5,000,000 public liability.
Related guides
- Blocked Downpipe at Ground Level or Drain Connection
When a downpipe blocks at the bottom: shoes, gullies and drain connections explained, how to tell where the blockage is and who to call for what.
- Unblocking a Downpipe from Above vs Below
When to clear a blocked downpipe from the gutter end and when from the bottom, the risks of each approach and why the gutter comes first either way.
- Leaking Plastic Downpipe Joint: Causes and Repair
Why plastic downpipe joints leak, how to tell a leak from a blockage, and what a repair involves, from reseating sections to replacing a split pipe.
- Moss Falling Into Gutters and Blocking Them
Moss falling from the roof into gutters causes blockages and overflow. Why it happens, why clearing alone doesn't last, and how to deal with the source.
Last updated 2026-11-03.