Who is responsible for drains in London?

Thames Water serves London and the Thames Valley and is responsible for public sewers and lateral drains beyond your boundary; drains serving only your home are yours (Ofwat, 2011).

Do I need a build-over agreement in London?

If you build over or within 3 metres of a public sewer in London, Thames Water requires a CCTV condition survey before granting one (Building Regs H4).

Are soakaways suitable in London?

Soakaways suit London's ground poorly in places — confirm with a BRE 365 percolation test.

Free to use No obligation UK-wide specialists Up to 3 quotes — you choose

London · verified local specialists

Septic Tank Installation in London

Installing or replacing a septic tank — correctly sized and sited to Building Regs, with the drainage field designed from a percolation test.

Free · No obligation · Under 2 minutes

Verified local specialists

In London and nearby

In short

Installing or replacing a septic tank — correctly sized and sited to Building Regs, with the drainage field designed from a percolation test. We match you with up to 3 verified local specialists in London — a shortlist, not the whole market, so you compare quotes without being bombarded. Local specialists know London's drainage and deal with Thames Water regularly.

Local to London

What drainage in London actually looks like

Your water company

Thames Water serves London and the Thames Valley. It's responsible for public sewers and the lateral drains beyond your boundary — including build-over agreements.

Who's responsible? →

Local ground conditions

Much of London sits on shrinkable London Clay — poor for soakaways and high risk for subsidence and root ingress. Clay-rich south-east England accounts for over 75% of UK subsidence cases (BGS / Geobear).

Soakaway rules & costs →

Local housing age

London has a very high share of pre-1919 housing — over half of homes in boroughs like Haringey (54.3%) and Kensington & Chelsea (65.1%) (Health Foundation, 2024). Older stock means older clay drains, so collapses and root ingress are more common.

Why drains keep blocking →

When to book

Blockages spike in December–January as festive fat and wipes hit the sewers (Water UK). Autumn is the best time to survey — before winter rainfall raises the risk of flooding and backing up.

Drainage questions in London

Get your London septic tank installation quotes

Up to 3 verified local specialists. Free, no obligation, under 2 minutes.

Get my free quotes

CCTV Drain Survey in London Blocked Drains in London Drain Repairs in London Drain Relining in London Soakaways & Surface Water in London Build-Over Survey in London Sewage Treatment Plant Installation in London Cesspit & Cesspool Installation in London Septic Tank Emptying in London Septic System Repairs & Servicing in London Percolation Testing & Drainage Field Design in London Septic Tank Compliance in London Who is responsible for drains?