Drainage, surfaces and lawn
Blocked drains: how to clear them and who is responsible
A blocked drain usually shows as slow draining, gurgling or a bad smell, caused by fat, wipes, roots or debris. You can often clear a single gully or downpipe yourself. Responsibility depends on location: drains inside your boundary are usually yours, while shared sewers are normally the water company responsibility.
- Also known as
- blocked sewer, clogged drain, drain blockage
- Easily confused with
- a collapsed pipe, a blocked gully versus a blocked sewer, a soakaway at capacity
- How serious
- Varies: a slow gully is minor, a backing-up sewer is urgent
- Typical cost
- Usually no cost for DIY control
How to identify blocked drains
The early signs are sinks, baths or toilets draining slowly, gurgling sounds, and a drainage smell outside near a gully or manhole. A fully blocked drain may overflow at the lowest point.
Locate the blockage before acting. Lift the nearest drain cover: if the chamber is full, the blockage is downstream of it; if it is empty, the blockage is upstream between the house and that chamber. This tells you whether it is one fixture, the private drain, or the shared sewer.
Common causes are cooking fat and grease, wet wipes and sanitary items, leaves and silt in outside gullies, and tree roots entering older clay pipes.
How serious is it?
Varies: a slow gully is minor, a backing-up sewer is urgent
A single slow gully is a minor nuisance you can usually clear. A fully blocked drain that backs up into the home or floods the garden with sewage is more urgent for hygiene reasons.
Repeated blockages in the same place can mean a more serious fault such as a collapsed pipe or root intrusion, which needs a camera survey rather than repeated clearing.
How to fix it yourself
- For a blocked outside gully, clear leaves and debris by hand (wearing gloves), then flush with water.
- For a blockage you can reach, use drain rods, pushing and turning clockwise so the rods do not unscrew and detach in the pipe.
- For sink and waste blockages, try a plunger or a hot water and washing-up liquid flush before chemical products, and avoid pouring fat down drains in future.
- If a chamber is full and the blockage is downstream towards the public sewer, contact your water company rather than rodding into the shared system.
- Disinfect and wash thoroughly after any contact with drain water.
When to call a professional
- The blockage is in the shared sewer beyond your boundary, or sewage is backing up into the home.
- Blockages keep recurring in the same spot, suggesting a collapsed pipe or root intrusion that needs a camera survey.
Who to call
- Your water and sewerage company first, as they are usually responsible for shared sewers and often clear them.
- A drainage specialist for private drains within your boundary, a camera survey, or root and collapse repairs.
Frequently asked questions
Who is responsible for a blocked drain?
Drains that serve only your property and sit within your boundary are usually your responsibility, while the shared sewer beyond it is normally the water and sewerage company responsibility. If you are unsure where the blockage is, contact your water company, which can advise and often clears public sewer blockages.
How do I unblock an outside drain myself?
Clear visible debris from the gully by hand with gloves, then use drain rods on a reachable blockage, turning them clockwise so they do not unscrew in the pipe. Flush with water afterwards and disinfect. If a chamber is full towards the public sewer, call your water company instead.
What causes drains to keep blocking?
Common causes are fat and grease, wet wipes and sanitary items, leaves and silt in gullies, and tree roots entering older clay pipes. Repeated blockages in the same place often mean a collapsed pipe or root intrusion, which needs a drainage camera survey rather than repeated clearing.
Sources
Editor, HomesAndHedge
Oliver leads HomesAndHedge's editorial coverage of home and garden problems. He researches and writes the plain-English explainers on pests, invasive plants, damp and mould, drainage and wildlife, drawing on guidance from bodies such as the Property Care Association, the RHS and the NHS, and is clear about when a job needs a qualified professional.
Last reviewed: 8 June 2026