The short answer
A blocked downpipe shows up as a gutter that fills and spills while the rain is still falling, a damp or stained wall below the outlet, or water backing up at the pipe's foot. Clear what you can reach from the ground and test with a hose. If the blockage is high up, packed hard or beyond reach, a ladder is not the safe answer and a roofer should do it.
The signs that point to the downpipe, not the gutter
A downpipe is the vertical pipe that carries water from the gutter outlet to the drain or a soakaway. Because it is a closed tube, a blockage inside it cannot be seen from outside, so you work it out from the symptoms.
- The gutter is full above one pipe. Water sits in the run and spills over the front edge near the outlet while the rest of the gutter is half empty.
- A damp or green stain on the wall directly below an outlet or a joint in the pipe, often with flaking paint or lifted render.
- Water coming out of a joint. When the pipe is blocked below, water pushes out at the nearest socket or bracket.
- Gurgling or a slow drain at the bottom, or a puddle that stays beside the pipe long after the rain stops.
- Frost damage. A cracked section in cold weather usually follows water that has been standing in a pipe that could not empty.
If water overflows along the whole run rather than at one outlet, the cause is more likely the gutter itself, and our page on overflowing gutters sorts out which one it is.
What blocks a downpipe
Leaves, moss and silt from tiles are the usual suspects. Moss washes off a roof in lumps, silt drifts down from concrete tile granules, and both settle in the gutter before they reach the outlet. The pipe is narrower than the gutter, so a small pile that the gutter tolerated can seal the pipe entrance.
The second group is things that arrive from outside. A ball, a nest of twigs from a gutter-side tree, a bird that has entered a pipe with a loose cover, or a wad of debris that slid in during a garden clear-out. A third cause is the joint itself: pipe lengths pushed together with a poor fit can leave a lip inside that catches debris, and a pipe bent where it has been fitted around a bay or a porch can slow the flow enough for sludge to settle.
The final cause is in the drain. If the bottom of the pipe discharges into a gully and the gully is clogged with silt or leaves, the pipe will back up even though it is clear itself. Look at the gully before blaming the pipe.
Clearing it safely from the ground
Start at the bottom and stay on your feet. If the pipe ends at a gully, clear the gully by hand, with gloves, and pour water in to check it runs away. Then run a hosepipe into the top of the pipe if you can reach the outlet from a safe, stable position, or push a flexible rod up from the bottom of the pipe.
- Use a drain rod or a plumber's flexible cable and work upward gently, not hard.
- Flush the pipe with water to see whether it runs freely.
- Collect the debris in a bucket so it does not wash into the drain.
Stop if the pipe is plastic and the blockage feels packed hard, or if the pipe is cast iron and old, because force can crack a joint. Do not use a pressure washer up the pipe; it can pop joints and drive debris into the gutter. Anything at first-floor height belongs to someone with a stable tower or scaffold, because a slip from a ladder is a serious risk for the sake of a handful of sludge.
When a roofer should do it
Call someone when the blockage is above first-floor level, when the pipe will not clear after a reasonable attempt, or when the wall is already showing damp. A roofer can reach the gutter and outlet together, clear both on the same visit and check whether the cause is deeper than a handful of leaves.
That check matters. A downpipe that blocks repeatedly may be a sign that the gutter is too shallow for the roof, that the outlet is too small, or that one pipe is serving a roof area it was never designed for. Our guide to one-piece gutters without joints explains how a continuous run reduces the number of places debris catches, and how that differs from a sectional system.
On an older house the pipe may be cast iron, and the answer usually means re-seating the pipe, not buying a new run. We would rather mend what has failed than sell more than the fault needs, and the photographs of what we found come with the written quote.
Stopping it happening again
Most downpipe blockages are a maintenance problem and the cure is routine. Clear the gutters before autumn leaf fall ends and again in spring, and check the outlets, not just the run. Overhanging branches drop more than leaves, so trimming them helps. A leaf guard or an outlet cage will keep large debris out of the pipe mouth, though it means a different pattern of checking, not no checking.
Look at the fixings too. A pipe held by brackets spaced too far apart sags, and a sag is a place for debris to collect. See our guide to gutter bracket spacing for the typical gaps. If the roof itself sheds a lot of moss or granules, a clean of the covering may reduce what ends up in the pipes; our roofline explained page shows how the parts fit together.
To have someone look, our gutters, soffits and fascias team can survey the run, photograph the outlets and send a written quote. Work we carry out is backed by a 10-year workmanship guarantee in writing, and any debris leaves with us. Ring 01793 626096 or message us on WhatsApp.