Who is responsible for a blocked drain — you or the water company?

A lot of homeowners pay for drainage work that the water company should have carried out for free. The rules changed in 2011 — most shared drains and lateral drains outside the boundary of your property were transferred to the local water and sewerage company under the Private Sewers Transfer — but plenty of homeowners still assume that any drain on their side of the fence is their problem. It often isn't.

The right first move when a drain blocks is to work out whose responsibility it is before any private engineer starts work. If it's the water company's, they cover it. If it's yours, you'll want an engineer you trust to give you a fair price. And if there's any ambiguity, evidence collected before the pipe is cleared makes the case far easier to argue. This is why we check first, quote second — see how we handle it below.

The dividing line is whether the pipe serves only your property or serves more than one property. Anything that only takes waste away from your house is your private drain, and it's your responsibility from the fixture inside the property all the way to the point it either connects to a shared sewer or crosses your boundary. Anything that serves more than one property, or lies outside your property boundary, is a public sewer — the water company's responsibility.

The most important addition to that rule is the lateral drain. Since 2011, the section of drain running from your property boundary out to the public sewer is a lateral drain and is the water company's responsibility, even though only your property uses it. So the boundary line for what you look after runs at the wall of your building for the internal pipework, and the property boundary line for the external run — not the point where the drain meets the main sewer.

Blockages in a shared drain that runs between multiple properties — for example, a terrace where several houses discharge into one common run at the rear — are the water company's problem. Blockages in the lateral drain (the section between your property boundary and the main sewer) are their problem too. Blockages in the main public sewer in the road itself, obviously, are theirs.

Signs it's shared or lateral: several houses on the same run are affected at the same time; a manhole in the road, pavement or a shared alley is the one that's full; sewage is coming up through gullies in more than one garden. In those situations, the water company must attend and clear it under their statutory obligation — free to you.

Every local water company runs a 24-hour flooding and blockage line. In the areas we cover, that's Anglian Water, Thames Water or Severn Trent depending on where you are. You call them, they attend. If they investigate and find it's actually a private issue, they'll tell you and you can call a private engineer then — but you haven't paid for something that wasn't yours.

Anything inside the four walls of your property is yours — sink traps, waste pipes, the run out to the manhole in your garden. External runs that only serve your property up to the boundary are yours (though as noted above, once they leave the boundary they're the water company's, even if they cross unadopted land before reaching the main sewer).

Signs it's a private issue: only your property is affected, the water backs up first at your own gully or manhole nearest the house, and nobody else on the street or terrace is having the same problem. In that case, a private drainage engineer is the right call.

Shared drains between two or more properties on the same run are joint responsibility until they cross the property boundary — and often the neighbours split the cost of any repair on that shared section. Historically these got contentious, but the 2011 transfer moved a huge number of them into the water company's ownership. For a shared run today, the most common outcome is that it's the water company's, not shared between neighbours — but you may need to call them out to confirm the layout.

Older properties, particularly Victorian terraces, sometimes have drainage arrangements that don't match any modern diagram — pipes that cross under other properties, shared soakaways, run-offs into old field drains. When the layout isn't obvious, a CCTV survey through the accessible chambers gives everyone something concrete to look at.

If you rent, day-to-day maintenance of things like clearing a hair-blocked bathroom drain often falls to you under the tenancy agreement. But structural drainage — everything from the fixtures out through the pipe network — is the landlord's responsibility under the Landlord and Tenant Act 1985. A blocked external drain, a collapsed pipe, or anything requiring engineering work is not a tenant repair. Report it to the landlord or letting agent; they arrange the works.

If the drainage is in a shared or lateral run outside the property, the water company remains responsible even in rented properties — the landlord isn't paying for public-sewer work.

Every job we go to starts with the same check — before we touch any equipment or quote for private work, we look at whether the water company should be dealing with it. If a manhole outside the property boundary is the one that's blocked, if it's a shared run affecting multiple houses, or if the symptoms point to the lateral drain, we tell you before starting private work and give you the water company's number. That's true whether you called us first or not. This is the same principle behind our Water Authority Partnership section on the homepage: making sure you don't pay privately for work the water company should have done for free.

If it turns out to be yours, we quote clearly, get on with the job, and leave you with photographic evidence of the cause. If it's genuinely ambiguous, we can produce a written CCTV report you can send to the water company to have them investigate before you commit to any private repair.