Blocked Outside Drain: What to Do and Who Pays

Lift the inspection chamber first

Everything follows from this. Find the drain covers on your property, usually a square metal or plastic lid in a path, drive or garden. Lift the one nearest the house, then the one nearest the boundary. If the chamber near the house is empty but the one at the boundary is full, the blockage is downstream of your property. If the near chamber is full and the far one is empty, it is between them and it is yours.

Clearing it yourself with rods

Drain rods are inexpensive and effective for a blockage within reach. Screw two or three sections together, feed them into the chamber towards the blockage, and add sections as you go. Turn them clockwise only, always, turning anticlockwise unscrews the joints and leaves a section in your drain, which turns a blockage into an excavation. Work with a plunger head first, then a corkscrew head if the obstruction is fibrous.

What is usually down there

Three things account for most outside blockages. Fat, oil and grease, which cool and solidify on the pipe wall and then trap everything passing. Wet wipes, including ones labelled flushable, which do not break down and knit together into a mass. And root intrusion, where a tree root has found a joint in an old clay pipe and grown into it, the classic recurring blockage that returns every year at the same time.

Who is responsible, and who pays

This is the part worth knowing before you call anyone. Drains inside your boundary serving only your property are yours to maintain. But lateral drains beyond your boundary, and shared drains serving more than one property, transferred to the water and sewerage companies in October 2011 in England and Wales. So a blockage in the shared run behind a terrace is very often United Utilities or Thames Water's responsibility, and they will attend at no charge to you. Ring them before paying a contractor.

When it keeps coming back

A drain that blocks in the same place repeatedly has a defect, not bad luck. Root intrusion, a displaced or cracked section, or a run laid with too little fall are the usual findings, and no amount of rodding fixes any of them. A CCTV survey identifies the cause and its exact position, and if it turns out to sit in a transferred public sewer, that footage is what gets the water company to repair it at their cost rather than yours.

Blocked Outside Drain: What to Do and Who Pays, your questions