Question answered
How to clear a blocked downpipe
The short answer
To clear a blocked downpipe, first confirm it is the pipe and not the gutter: water spilling from the outlet or running down the wall in rain gives it away. From the ground, check the shoe or drain at the bottom, then try flushing with a hose. Do not climb above a safe ladder height or lean out sideways. If the blockage will not shift, or the pipe is cracked, call a roofer.
A blocked downpipe turns a working gutter into a full one. Most checks can be made from the ground, and the safest clearance often starts at the bottom of the pipe, not the top.
Signs that the downpipe is the problem
A blocked downpipe shows itself in rain. Water backs up in the gutter above and spills over the front near the outlet. The pipe may overflow at a joint halfway down, or stay full for hours after the rain has stopped, and you may hear gurgling. At the foot, the drain or gully stays dry while the gutter overflows.
Winter adds a further sign. A pipe that is left holding water through a hard frost can freeze solid, and the ice then splits a seam or pushes a joint apart. That is one reason to deal with a standing blockage early, before the weather turns.
Do not assume the pipe is at fault without checking the gutter. A spill along a whole run means size or fall; one patch at the outlet means a blockage. Our page on why gutters overflow helps tell them apart.
Safe checks from the ground first
Start at the bottom. Lift off the grating over the gully, check for leaves, silt or a fallen tile, and look at the shoe, the angled section where the pipe meets the drain. Many blockages sit here, where debris washed down the pipe has dropped out.
Run a hose gently into the top of the pipe if you can reach it from a stable position at a safe height, and watch the base. Water flowing freely is a good sign. If it backs up, the blockage is somewhere in between.
Tap down the pipe with your knuckles. A dull sound can point to the choked section. Never use a pressure washer on a downpipe, which can force joints apart and drive water into the wall. The same goes for poking about with a long wire, which can scratch plastic and split old cast iron. Wear gloves and eye protection when clearing wet debris, and keep a bucket on hand.
Clearing the pipe with simple tools
If the blockage is at the top, a trowel or gloved hand from a ladder is the method of choice. Only try it when the ladder is footed and tied and you can reach with both feet on the rungs, one hand for the work and one for the ladder. If it needs a lean, stop.
For a blockage lower down, a plumber's flexible rod or a length of garden hose with a spray head will often push it through. Work from the bottom upwards if the pipe will take it, and pull the debris out rather than pushing it deeper.
Moss balls from the roof are a common cause. They swell when wet and wedge at a bend. Once the pipe is clear, flush it well and watch the rain run through. Fitting a leaf guard at the outlet sometimes helps, though our answer on gutter cleaning explains why the gutter still needs a look every year.
When to stop and call someone
Call a roofer if the blockage will not move, the pipe is cracked or leaning, a bracket is loose, or you cannot reach it without overstretching. Tall houses, bays, flat roofs and conservatory runs need a tower or a cherry picker, not a domestic ladder.
Look at the pipe material too. Old grey cement downpipes can be asbestos cement. HSE says to treat buildings built before 2000 as possibly containing asbestos, and that asbestos cement is non-licensed work only when handled carefully without breaking it up. Do not drill, scrape or snap an old pipe. If you suspect it, stop and ask.
If a downpipe has a long internal blockage, we can usually clear it and check the joints at the same time. Our written quote comes after a visit, with pictures of the inside of the pipe, the shoe and the gutter outlet, so you see the blockage for yourself.
Stopping it happening again
Cut back overhanging branches, remove moss from the roof edge, and clear the gutter before autumn and after storms. A wider-mouthed outlet or a continuous aluminium run has fewer joints to snag debris, which our guide to seamless aluminium gutters describes.
Brackets matter as well. A downpipe needs fixing at regular intervals, and a pipe that has pulled away from the wall develops kinks that catch debris. For gutters, bracket spacing is worth checking when you replace a run.
If the same pipe blocks every few months, something upstream is feeding it: a broken tile, a mossy valley, a roof that is shedding grit. That is a roof problem as much as a gutter one, and we look at both in the survey. The wider gutters, soffits and fascias hub shows how the pieces fit together, and the downpipes guide covers sizes and materials.
Downpipes and drains
Can I pour boiling water down a blocked plastic downpipe?
It is better not to. Boiling water softens uPVC and can distort joints, and it is hard to pour from a height safely. A hose, a flexible rod and patience work better, and they do not risk a scald or a warped pipe.
Why does my downpipe overflow at a joint halfway down?
That usually means the pipe is blocked below the joint, so water backs up and finds the weakest point. It can also mean the joint has pulled apart or the clip is missing. Clear the blockage first, then check that the sections still push fully into each other.
Tell us about your roof
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