Pest Control
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Rats inside a house are bad enough. When they keep coming back after treatment and nobody can find a hole in the outside wall, the missing piece is often below ground. Brown rats live in drains and sewers, and a defect in a property's drainage can give them a hidden route straight into the building.
Why rats live in drains
The brown rat (Rattus norvegicus) is sometimes called the sewer rat for good reason. Sewers and drains give it shelter, a steady temperature, water and a network of routes linking streets, gardens and buildings, and the more built-up an area is, the more likely rats are to be living in the sewers beneath it.
Rats are well suited to this life. They are strong swimmers and good climbers, and they can squeeze through any gap they can get their head through. A drainage system in good repair keeps them inside the pipes. The trouble starts when there is a way out.
How rats get from a drain into a house
Common defects include:
- cracked or collapsed underground pipes
- displaced or open pipe joints, often where tree roots or ground movement have shifted them
- broken inspection chambers and damaged or ill-fitting covers
- old pipes left open and unused after building work
- redundant connections left behind when a kitchen, bathroom or toilet was moved
The rat does not usually come up through a sink or toilet. More often, a defect below the building lets it into a floor void or wall cavity, and it travels from there. That is why scratching under the kitchen floor can be some distance from where the rat first got in.
Can a rat come up the toilet?
It can happen, though it is uncommon. Rats can swim and hold their breath, and a rat in a damaged or poorly connected soil pipe can occasionally make its way through the U-bend. If it does happen, close the lid, put something heavy on it and call us. A rat in the toilet is a strong sign of a drainage defect that needs investigating, not a one-off.
Can building work create a route?
Yes, and it is a recurring cause of rat problems. Extensions, kitchen refits, new bathrooms and garage conversions all involve changes to drainage. A pipe that is no longer needed should be capped and sealed, not simply abandoned beneath the new floor. The problem may not show for months or years, until a rat finds the opening. If activity is concentrated around an extension or an altered part of the house, the building's history is a useful clue.
Signs the drains may be involved
No single sign proves it, but these patterns make it worth investigating:
- rats returning repeatedly after treatment
- no obvious entry point found on the outside of the building
- activity under floors, or close to kitchens, bathrooms and toilets
- noise in wall or service voids
- activity around an extension or an area that has been altered
- damaged or loose drain covers, or known drainage problems
- disused toilets, gullies or old waste pipes on the property
The first step is still a full pest survey. Rats can get in through a gap of about 15mm, and the more ordinary routes (gaps around pipes, damaged air bricks, gaps under doors and at the roofline) need ruling out before anyone recommends a drain investigation.
When a CCTV drain survey helps
Where the evidence points underground, a drainage contractor can run a camera through the pipework to look for cracks, displaced joints, hidden chambers and redundant connections that cannot be seen any other way. It is a valuable tool, but it is not the first step for every rat problem. It makes sense once a pest survey has found reasonable grounds to suspect the drains.
The two trades do different jobs. We confirm the rats, assess the infestation, trace their movement, treat them and recommend proofing. A drainage contractor surveys and repairs the pipes. Some repairs need excavation; others can be done by lining the pipe from inside. The drainage contractor will advise on that.
Who is responsible for the repair?
It depends where the defect is. As a general rule, a drain that serves only your property and lies within its boundary is the owner's responsibility, while public sewers and many shared or lateral drains are the responsibility of the local sewerage company. The exact position varies with the pipe and its location, so once a defect is found, the drainage contractor or sewerage company should confirm who is responsible before work starts.
Things not to do
- Do not go into manholes or open chambers. Drains can hold harmful gases and contamination, and they are confined spaces. Leave inspection to professionals.
- Do not rely on poison. Adding more bait without fixing the defect leaves the route open for the next rat, and a rat that dies in a void can leave a smell that lasts for weeks. Our guide to dealing with dead rodents explains why.
- Do not ignore food sources. Bins, bird feeders and compost help keep rats in an area even when the route is underground.
Rat urine can carry leptospirosis, so avoid contact with any water or surfaces rats may have used, and wash your hands after working outside. Our clean-up guide covers what to do once the rats have gone.
When to call us
If you are finding signs of rats under floors or in wall voids, or they have come back after a previous treatment, call us. We survey the property, deal with the rats inside and trace how they are getting in. Where the evidence points to the drains, we will tell you so and explain what to ask a drainage contractor to look for. See our rat control page, or call 01926 632 929.