A recent client explained that they were hearing noises in the walls and that there was, occasionally, a slightly ‘sewery’ smell in the living room. It was time to take a look in the inspection chamber. The CCTV showed us one rogue branch connection that didn’t appear to be used – it was bone dry and rather dusty-looking. After a series of flush tests, we couldn’t work out what it was connected to so opened up the void under the stairs, the nearest location we could reasonably get to and in direct line of the pipe’s pathway.
Peering in through the rectangle we’d cut out, we found this hole in the floor: the other end of the sewer pipe. Clearly, this isn’t capped off (closed) and would allow rats free access to the under-stairs space. But how were they then getting into the walls? That was obvious by looking up and left of the open pipe….
Here we can see the hole in the wall that leads directly to the cavity (and then on to the loft, other walls and so on). The black mark running down the wall is rat body grease, suggesting this route has been used for a fairly long time.
Now we know how the rats are getting in, we can plan a cure: install a drain bung (a stopper) to close off the pipe at the chamber end, trap out any rats that might be in the building and then make good the hole we made getting into this space.
Why was an open sewer left under the stairs? We later found out that the house was originally planned as a three story townhouse but, as building started, the developer switched the design to become a two story terrace. Of course, the groundwork would have been the first thing the construction crew created – and the original design would have had the soil stack running up the building in this location. All the way back in 1970 or so, someone forgot to close off the unused, open pipe – and in 2022 the problem was finally solved once and for all.