“We’re hearing noises in the loft” was the initial call out and a quick look revealed rat droppings spread around in the insulation. Rats typically get into loft spaces via the cavity walls so the next place to check was outside, making sure there’s no obvious sign of entry through a faulty air-brick or a rat burrow. If there’s nothing obvious then the chances are entry is via the foul sewer so the next check is to look in an inspection chamber for evidence. On this occasion, we felt it was worth putting a CCTV camera into the pipe and, sure enough, when we got to the rest bend (where the pipe changes from the horizontal plane to the vertical) we were met with this image
This shows plant roots growing down the pipe – the small dot of white in the centre is the top of the soil stack and is way up on the roof, we’re looking vertically upwards.
The fix is to dig down to the rest bend and repair it but, for now, we’ve fitted a one-way valve in the chamber to stop any more rats getting in.