“Drain” and “sewer” are often used as if they mean the same thing, but in UK drainage terms they describe different parts of the system, and knowing which one you’re dealing with can affect who’s responsible for sorting out a blockage.
What counts as a drain
A drain is the pipework that serves a single property, carrying wastewater from that property’s sinks, toilets and other fixtures to the point where it connects with pipework from other properties. If the blockage is within your own pipework, it’s almost always your responsibility to have it cleared.
What counts as a sewer
Once a drain joins pipework serving more than one property, it becomes what’s known as a lateral drain or, further along, a public sewer. Public sewers are generally the responsibility of the local water company, following changes to ownership rules that transferred most private sewers to water company ownership.
Why the distinction matters
- A blockage in your own drain is usually your cost to clear
- A blockage in a shared lateral drain may need agreement, or investigation, with a neighbour
- A blockage in the public sewer is generally the water company’s responsibility, though you’ll often need a survey to prove where the fault actually lies
Our full breakdown of who to call for a blocked drain covers this in more detail, including how the boundary is usually worked out.
Why it’s hard to tell from the surface
In practice, most people can’t tell whether a blockage is in their own drain, a shared lateral, or the public sewer just from where the symptoms show up. Water backing up in a downstairs toilet, for example, could point to a blockage close to the house or one much further down the system. Guessing wrong can mean calling the wrong organisation and losing time while the problem sits unresolved.
How to find out for certain
A CCTV drain survey traces the exact route and condition of the pipework, showing clearly where your responsibility ends and, if relevant, where the water company’s begins.
If you’re not sure what you’re dealing with, call us on 0333 200 1623 and we’ll help you work out whether it’s a drain issue, a sewer issue, or something in between.