Rats live in sewers, and they only reach your property when the drain between the sewer and your home gives them a way through: a broken pipe, a displaced joint, an unused branch or a chamber wall they can climb. A rat flap, also called a rat blocker or non-return valve, is a stainless steel flap fitted inside the drain that lets waste and water flow out but stops anything travelling back up. We fit them after a CCTV drain survey has shown where the rats are getting in. Call 07427 195142 to talk it through.
How rats get from the sewer into your home
Rats are strong swimmers and climbers, and a surprising number of drainage faults suit them. A cracked pipe or open joint gives them a route out of the sewer and into the soil around your foundations. An old unused branch — common where a drain has been altered over the years — makes a ready-made runway. From there they can reach wall cavities, under-floor spaces and, in the worst cases, come up through a toilet, which is how most people first realise there is a problem.
The important point is that rats in drains are a symptom. If the pipe were sound, they would stay in the sewer. That is why fitting a flap without looking at the drain first is only half a job.
Survey first, then fit
Before fitting anything, we put a camera down the run. The survey shows whether the pipe is broken or displaced, whether there are redundant branches, and which direction the rats are travelling. If the survey finds a structural defect, the right fix may be a drain repair or no-dig patch rather than, or as well as, a flap — sealing the hole removes the route altogether.
Where the pipe is sound but the property keeps getting visitors — some homes simply sit on a run that rats favour — a rat blocker in the chamber or in the pipe is the sensible answer.
What a rat flap is and how it works
A rat flap is a one-way gate, usually stainless steel, installed in the drain or the inspection chamber. Waste and water push it open on the way out and it closes behind them, so nothing can come back the other way. It has no moving parts to wind up and nothing to poison or bait. Because it sits in the drain line, it protects every fitting connected upstream of it — toilets, basins, showers and floor gullies alike.
The flap must be sized to the pipe and fitted the right way round, seated so it cannot catch wipes and debris. A badly fitted flap can cause blockages, which is why it goes in after a survey and gets checked on camera afterwards.
What a rat blocker will not do
A flap stops rats travelling up the drain; it does not deal with rats already inside the house, and it does not fix a broken pipe. If there is an active infestation indoors, that is a job for pest control, and we will say so. Our part is the drainage side: finding the route, closing it, and fitting the flap so the drain stays a one-way street.
Keeping it working
Rat flaps are low maintenance but not no maintenance. Debris can catch on the hinge, so an occasional check — often combined with a look while other drainage work is done — keeps it clear. If you ever have the drains jetted or surveyed, mention the flap so it can be inspected at the same time.
Questions
Will a rat flap stop rats coming up the toilet?
Yes, if the toilet is upstream of the flap. The flap closes the drain against anything travelling back towards the house, which is the route rats take to reach a pan.
Why do I need a CCTV survey before fitting a rat blocker?
The survey shows how the rats are getting in. If the pipe is broken, repairing it may be the real fix, and the flap needs to be sized and positioned for your specific drain.
Can a rat flap cause a blockage?
A correctly sized and fitted flap should not. A poorly fitted one can catch debris, which is why we fit on camera evidence and check the installation afterwards.
What affects the cost of rat blocker installation?
Mainly access and pipe size: a flap in an accessible chamber is simpler than one fitted inside a buried run, and a survey is usually needed first. We price it once we have seen the drain.