How rats use drains
Brown rats swim well, climb inside pipes and can squeeze through surprisingly small gaps. They travel through sewers and private drains and come up wherever the system is damaged or open.
Common drain defects that let rats in
- Cracked or collapsed clay pipes under gardens and floors
- Redundant connections left open after a kitchen, bathroom or WC was removed or moved
- Missing or broken inspection chamber covers
- Displaced joints where tree roots have pushed pipes apart
- Uncapped pipes in extensions and lofts conversions
Signs of a drain-related rat problem
- Rats appearing repeatedly in the same place despite treatment
- Rats near manholes, gullies or the base of soil pipes
- Noises under the floor, in walls near the bathroom or in the boxing around soil pipes
- Burrows next to drain runs in the garden
What we do
- Lift inspection chamber covers and look for signs of rat activity and defects
- Treat rats that are above ground or in the building
- Fit rat blockers (non-return valves) where the drain is suitable, so rats cannot travel upstream
- Recommend a CCTV drain survey and repairs if pipes are broken
Who is responsible for drains?
In England, private drains serving only your property are generally your responsibility. Shared lateral drains and sewers transferred in 2011 are usually the responsibility of the water company, which for most of South London is Thames Water. If you think a public sewer or shared drain is damaged, contact the water company.
Questions and answers
Can rats come up through the toilet?
It is rare, but possible where drains are defective. A rat blocker in the drain prevents it.
Do rat blockers affect my drains?
No. They are designed to let waste flow out normally while stopping rats travelling back up.
Who fixes a broken drain?
Private drains serving only your property are usually the owner's responsibility; shared drains and public sewers are usually the water company's.
Related pages
This page is general information, last reviewed on 19 October 2026. It is not a substitute for an on-site inspection.