I'm surprised by what I am reading here. You can't just build over the sewers or lateral drain lines. You have to apply to utility companies for permit to divert public sewer line under Section 185 of the Water Industry Act 1991.
Actually, you might not have to divert anything, so long as we can still gain access to our manhole. We have a whole department covering build-overs... they're called the "Build-Overs Department".
I don't know of any utility company that will even discuss scenario where a vital part of drain, let alone manhole or chamber would be linteled/concreted/built over and end up underneath or inside a building.
Or a train station, or an airport, or a hospital... And yet, we do all that and more - Talk to Developer Services. They will advise you.
What happens if at some point down the line they need to repair/replace the pipe and its under your property?
If you didn't obtain permission to build over it, we *technically* have right of access under Section 159 of the WIA to come in and rip up your nice new kitchen floor, before billing you for an illegal build-over... Chances are we'll work toward a very amicable solution, though!
The enforcement of S159 notices tends to be more for the bigger water pipes and sewers, usually under emegency works where the risks include things like death.
If it's your own drain, the utility company won't care
But the process of establishing ownership is far more complicated than just whether or not it serves more than one property. There's a whole boundary thing now, among other factors. We got a rather thick reference manual on it!
Depending on where you are, you might even find you pay one company for services facilitated by another water company's assets, so you end up talking to the latter instead.
End of the day, the advice is still - Talk to the Developer Services at your local water company, who will tell you *exactly* what the score is and what you must do (including any building standards).
