Clearing a blocked outside drain
Check the steps below first — if you're not confident, get it fixed safely today.
Post a job — we'll find you an engineer →Outside drains block more often than you'd think, especially in autumn when leaves and debris accumulate, or after heavy rainfall when silt builds up in the pipes. Most UK homes have a network of gullies and inspection chambers (manholes) that form the first line of defence before waste water reaches the public sewer — and when these get clogged, you'll notice water pooling around your garden, patios becoming waterlogged, or unpleasant smells near downpipes. The good news is that many blockages are straightforward to clear yourself without calling out an engineer, though knowing when to stop and bring in the professionals is just as important. This guide walks through the practical steps to diagnose where the blockage sits and what you can safely tackle. If you've cleared the accessible bits and water's still backing up, or if you suspect the problem lies on the shared public sewer, it's time to contact your water company or a drainage specialist.
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Most likely cause & what to check
First check the gully drain — the grid at ground level near a downpipe or path. Lift the grid and scoop out any leaves and silt by hand (wear rubber gloves). Flush with a hosepipe.
Lift the nearest manhole cover. If it's full of water, the blockage is further downstream. If empty, the blockage is between this point and the previous chamber.
If the gully is clear but the drain is still blocked, call a drainage company — they have the specialist rods and jetting equipment. If it's on a shared sewer, call your water company (e.g. Thames Water) — it's their responsibility and they'll fix it free.
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Frequently asked questions
What's the difference between a gully and a manhole?
A gully is the small grid you'll see at ground level, usually near a downpipe or at the edge of a path — it's your first drainage point. A manhole (or inspection chamber) is the larger covered access point deeper in your garden or driveway, allowing you to see into the main drain run and identify where blockages sit.
How often should I clean my outside drain to prevent blockages?
A quick check of your gully every autumn and spring helps catch leaves and silt before they cause problems — usually takes 10 minutes. If you have trees overhanging your property or live in a particularly wet area, monthly checks during autumn are a sensible precaution.
Is a blocked outside drain always my responsibility?
Drains up to your property boundary are your responsibility; anything beyond that on the public sewer belongs to your water company and they'll clear it free of charge. It's worth checking your property deeds or asking your water company where the boundary sits if you're unsure.
Can I use chemical drain cleaners on outside drains?
Whilst shop-bought cleaners might shift minor blockages, they're less effective on outside drains clogged with leaves and silt, and can harm the environment. Manual clearing with a hosepipe or professional jetting is far more reliable and safer for your pipes and local watercourses.