Rat Blocker Fitted to a Drain in Cambridge

When rats keep appearing in a house with no gap anyone can find, the drains are the usual suspect. Brown rats live in the sewer network, and where a private drain connects to it, they can travel up into the pipes serving a property. A rat blocker is one way of stopping that journey.

What a Rat Blocker Is

A rat blocker, sometimes called a rat valve or non-return valve, is a stainless steel or plastic fitting with a hinged flap. It sits inside the drain pipe, usually where the pipe leaves an inspection chamber heading towards the sewer. Water and waste push the flap open as they flow away. A rat trying to come the other way meets a closed flap it cannot push or gnaw through.

Fitted in the right place, it cuts the property's drains off from the rats in the sewer beyond, while the drains carry on working normally.

When a Blocker Is the Right Answer

• Evidence points to rats arriving from the sewer, such as droppings or debris in an inspection chamber.
• The property's own drain run is in reasonable condition, or its defects are upstream of where the blocker will sit.
• There is an accessible inspection chamber in the right position to fit it.
• Treatment has already dealt with the rats inside the property.

When It Is Not

A blocker is not a repair. If the drain between the house and the chamber is cracked, has a displaced joint, or has an old connection left open under a floor, rats already in that section can still reach the house, and a blocker downstream does nothing about it. Likewise, if rats are getting in through a gap in the wall or a shared loft, the drain is not the route at all.

Where we suspect a defect, the next step is usually a camera survey of the drain by a drainage contractor, followed by a repair if one is needed. We say so plainly rather than fitting something that will not solve the problem.

What This Kind of Job Involves

• Survey. We look at the property inside and out, lift the inspection chamber covers and check for signs of rats using the drains.
• Treat first. Any rats already inside the property or its voids are dealt with before the drain is closed off.
• Decide on the fix. A blocker where the evidence and the drain layout support it; a referral for drain survey or repair where they do not.
• Fit and check. The blocker goes in at the chamber, and we check that the flap moves freely and the drain flows.
• Follow up. We confirm that activity in the house has stopped.

We confirm the work and the price before anything is booked, and there is no call-out fee.

Looking After a Rat Blocker

A blocker has a moving part in a drain, so it needs the drain to be treated sensibly. Wipes, fat and other items that should not be flushed can catch on the flap and hold it open or cause a blockage. If you have a blocker fitted, lift the chamber cover now and then and check it is clear. If the drain backs up, tell whoever clears it that a blocker is fitted, so it can be removed and refitted rather than damaged.

Price and Next Steps

Rat control is £260, and the rat control cost guide explains what the treatment covers. Gaps above ground are dealt with by rat and mice proofing, at £180 for up to 1 hour, with any further time quoted before it is carried out. The rat control service page describes the whole approach. If rats have come back after an earlier treatment, our post on why rats return is worth reading, and how rats get into a home covers the other routes.

Treat the rats on your side of the pipe, then close the door on the rest.