Blocked drain in a block of flats: who is responsible

In a block of flats, who deals with a blocked drain depends on where the blockage is. A pipe that serves only one flat is usually that flat owner’s responsibility. Drains inside the block’s boundary that serve more than one flat are usually the freeholder’s or the management company’s, and sewers outside the boundary are Thames Water’s.

Three stretches of pipe

Drainage from a block falls into three parts:

1. The flat’s own branch: the waste pipes from its sink, bath, shower and toilet, up to where they join a shared pipe. This is usually the flat owner’s responsibility, as the lease sets out. If the flat is rented, the landlord is responsible, so a tenant reports it to the landlord or letting agent.
2. Communal drains inside the boundary: the soil stacks, shared pipes, gullies and manholes that serve more than one flat. In a private block these are normally the freeholder’s or the management company’s to maintain. In a converted house with no management company, council guidance says pipework shared by two or more flats is usually the joint responsibility of the flat owners.
3. Sewers outside the boundary: Thames Water’s, as the sewerage company for London.

What changed in 2011

On 1 October 2011, private sewers and lateral drains (the stretch of drain between a property’s boundary and the sewer) that were connected to a public sewer on 1 July 2011 passed to the water companies, under the Water Industry (Schemes for Adoption of Private Sewers) Regulations 2011. In London that means Thames Water. Before then, the owners of the properties a private sewer served were responsible for maintaining it.

The transfer stopped at the boundary of each property. The government guidance on the transfer treats a residential building with several flats as a single property, and gives each block in a development of several blocks its own boundary. Drains inside that boundary stayed private, and the guidance says the water company did not become responsible for the internal, communal drainage of the building.

Who pays

• The flat owner pays for clearing their own branch, or the landlord does if the flat is rented.
• Clearing and maintaining communal drains is a building cost, usually paid through the service charge in the shares the leases set.
• Public sewers and lateral drains are Thames Water’s. The same guidance says an occupier has no authority to commission work on a public sewer or lateral drain without first contacting the water company, so report a blockage there to Thames Water rather than sending in a contractor.

Working out where the blockage is

• One flat’s sink, bath or toilet is slow, and nobody else’s is: the blockage is probably in that flat’s own branch.
• Several flats are affected, or a gully or manhole inside the boundary is overflowing: the communal drain is the likely place.
• Neighbouring buildings are affected too, or a manhole in the street is full: the blockage is likely to be in the public sewer, so report it to Thames Water.

The FAQ on who is responsible for a blocked drain gives the same split in short.

Keeping communal drains clear

Fat poured down sinks and wipes flushed down toilets both build up in drains, so a notice to residents about what goes down the sink and the toilet helps. A drain that blocks again and again usually has a cause in the pipe, such as scale, roots or a damaged section, and a camera survey can locate it. See why a drain keeps blocking.

Neos Engineering clears communal drains in residential blocks across all of London, 24 hours a day, traces blockages that keep coming back, and plans drainage maintenance for a building or a portfolio. See work for block managers, blocked drains, or contact the office.

If you need us

• Work for block managers
• Blocked drains in London
• Commercial drainage