Thames Water . . . Insiders guide . . .

The pipe that exits your house is called a drain. If this drain then joins a drain from another property, the pipe becomes a sewer from that joint onwards.

In rented properties the landlord has overall responsibility for arranging clearance, but it is reasonable for tenants to carry out simple tasks like keeping gulley gratings free from leaves and not letting food wastes, fat or oil get into the drain.

When a drain serving one property joins with a drain from another property, the shared pipe is known in law as a sewer. Where the premises were built before 1 October 1937 the sewer is nearly always a public sewer. Those built after that date are usually private sewers.

Responsibilities for unblocking or repairing problem sections of foul sewage systems depend upon whether or not the sewer is classed as private or public. However this is not always easy to determine.

Private sewers (ie built after 1937) are maintained jointly by the owners of the properties which they serve. So the owner of a post-1937 property would be wholly responsible for their own drain and, if that drain does not connect directly to a public sewer (probably the main sewer under the road), they would share a further responsibilty with other owners for a private sewer, up to its connection onto the public sewer.

Each owner is only responsible for sharing the maintenance of the private sewer downstream of their connection into it. So a blockage at the downstream end of a private sewer serving a terrace of houses should be cleared and paid for jointly by all of the owners, while a blockage at the upstream end would fall only to the two owners at that end. If the owners cannot clear the blockage themselves then they need to call in a drain cleaning company.