Blocked Drain: Who Is Responsible – You, Your Neighbour or South West Water?

Reviewed by the DCI Drainage team · Last updated September 2026

Few things start a neighbourly dispute faster than a blocked drain and an unclear bill. The rules in England are actually fairly tidy once you see them laid out, and knowing them can save you a callout charge altogether. This guide explains who owns what, how the 2011 transfer changed things, what South West Water will and will not do, and how to work out where a blockage sits before anyone pays a penny.

Drains, lateral drains and sewers: what you own

The word "drain" gets used for everything, but responsibility turns on three legal categories. A drain is a pipe serving a single property, within that property's boundary: yours to maintain. A lateral drain is the continuation of that pipe once it leaves your boundary on its way to the sewer: the water company's. A sewer is any pipe carrying waste from more than one property: almost always the water company's too. The moment your pipe either crosses the boundary line or picks up a neighbour's flow, it usually stops being your problem.

Here is the same thing as a quick reference table.

The 2011 transfer, and why it matters

Before October 2011, homeowners were jointly responsible for long runs of shared pipework, and blockages in a shared drain meant awkward conversations about splitting the bill. The law then transferred most private sewers and lateral drains to the water and sewerage companies across England and Wales. Overnight, pipework that several households used to co-own became the water company's to maintain.

Fifteen years on, plenty of homeowners still do not know this, and some end up paying a private firm to clear a blockage that the water company would have dealt with for nothing. The rule of thumb since 2011: if the pipe is shared with any other property, or lies beyond your boundary, it is very likely the water company's. The main exceptions are pipes that never connected to a public sewer at all, such as those running to a private septic tank or treatment plant, which remain entirely private.

What South West Water is responsible for

Across Cornwall, Plymouth and the rest of Devon, the sewerage company is South West Water. If a blockage sits in a public sewer or lateral drain, clearing it is their job, at their cost. If sewage is escaping from one of their pipes, that is also theirs to deal with, and worth reporting promptly.

What they will not do is clear a private drain inside your boundary, however sympathetic the person on the phone may be. They will also not generally repair private pipework, even where their own investigation found the fault. So the practical sequence when a drain backs up is: work out roughly where the problem is first, then call the right people. Ring the water company for a blockage that is theirs, and a local drainage firm for drain unblocking on a private run.

One honest note from our side of the fence: a reputable independent will tell you when a job is the water company's rather than charge you for it. If an engineer lifts a cover, finds the public sewer surcharged and still wants to bill you for clearing it, get a second opinion.

Working out where the blockage is

You can narrow down a blockage's location yourself in ten minutes with nothing more than a screwdriver to lift inspection covers, and it is worth doing before you call anyone.

Read the chambers

Lift the inspection chamber covers on your property, starting nearest the house. The logic is simple: a chamber standing full of water means the blockage is downstream of it, towards the sewer. A chamber that is empty and flowing means the blockage is upstream, back towards the house. If your last chamber before the boundary is clear but waste is still backing up indoors, the problem is inside your own pipework. If that final chamber is full, the blockage may well be beyond your boundary and therefore the water company's.

Ask the neighbours

If next door's toilets are gurgling and their gullies are backing up at the same time as yours, you are almost certainly looking at a blockage in a shared or public section. One property affected on its own points to a private drain.

Get eyes inside the pipe

Where the covers do not settle it, or a blockage keeps returning, a CCTV drain survey answers the question definitively. The camera records exactly where the problem is, what is causing it, and which side of the boundary it sits on. That recording is solid evidence if you need to show the water company the blockage is in their pipe, and it tells you whether a recurring blockage is really a defect that needs a drain repair rather than another clearance.

Shared drives, rented homes and older properties

A few situations catch people out. On a shared private drive or in a small close, the drains can run under several gardens before reaching the road, and the 2011 transfer usually means the shared spine is the water company's even though it crosses private land. In rented homes, drain maintenance generally sits with the landlord, though a tenant who caused the blockage by flushing wipes or pouring fat away can fairly be asked to cover it. And in parts of rural Cornwall and Devon, plenty of properties drain to a septic tank or private treatment plant rather than the mains: everything on those systems is private, all the way, so the water company will not attend at all.

Older properties bring one more wrinkle: maps are often wrong or missing. Victorian terraces in Plymouth, for example, sometimes have rear drains running under whole rows of gardens in arrangements nobody has documented. Where ownership genuinely cannot be agreed, a camera survey and a measured plan of what is actually underground is usually what settles it.

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