Who's responsible for a blocked drain — me or the water company?

Since 2011 the rules in England and Wales are pretty clear, but most homeowners still don't know them. In short:

Your responsibility

The pipework inside your property boundary that only serves your home. This is usually:

• Internal soil and waste pipes
• The branch drain from each fitting
• The collector drain up to the boundary of your property

The water company's responsibility (the 'lateral drain' and shared sewer)

• The drain run between your property boundary and the public sewer (the lateral drain)
• Any shared sewer that serves your house plus a neighbour's

This transferred to the water companies (Thames Water, Southern Water, etc.) in October 2011 under the Public Sewer Transfer.

How to find out which it is

1. Lift the manhole nearest the property boundary.
2. If it's clear and the blockage is upstream of it (towards your house) — your problem.
3. If it's full of standing waste water and the next downstream chamber is also blocked — almost certainly the water company's.

What to do if it's the water company's

Call them directly — the number's on your water bill. They'll usually attend within hours for free. Don't pay a private drainage firm to clear a sewer blockage that the water company is legally on the hook for.

Exceptions and grey areas

• New build estates sometimes have private drainage retained by the developer or a management company. Check your deeds.
• Septic tanks and treatment plants are always the property owner's responsibility, including the run to the tank.
• Surface-water-only drains (gullies, downpipes, soakaways) are usually the property owner's responsibility even past the boundary.

When in doubt, lift the chamber and look. Five minutes can save £200.