We are planning an extension – we have an inspection chamber just outside the existing conservatory, which when the build is complete will be inside the extension – we are planning to move it just outside, however it is not always that easy depending on what you are looking to do. Our existing drains run under the garage and the slab, so moving the inspection chamber means moving the whole run about 4 meters further out and moving 2 existing inspection pits.
I forget how exactly I who I spoke, but I’m pretty certain the relevant water board can tell you if the drain is shared or not. I don’t remember paying for this. Ours isn’t shared with our neighbours.
Our drains are however both rainwater and grey water, which I’m told is no longer okay, and we need to build a soakaway for the rainwater now as well.
Nightmare when you start getting into this stuff
On the rats point, I cant see the relevance. If the rats are in the sewer, the only way they can get into your house from the drains is via the toilets, which you all have, they can’t get through a sealed cover. I will caveat, as we had rats in the garden, and digging them out, I found the nearby inspection chamber had a crack in it (its about 2m deep, right near the cover). So I filled with steel wool and concreted. No more rats. Till maybe they swim up the waste pipe….