Thanks for the replies so far. Quick update:
- I have spoken to the water company and they've confirmed that I do have space to put the new man hole in front of the existing house, but I may be required to perform a small amount of underpinning to the existing foundations (just in the vicinity of the new man hole). Because the drains are on private land, the water company and local authority don't care whose land or which buildings they run under, as it's outside of their remit.
- Building a new drain under the existing house is entirely possible engineering-wise and structurally but it's expensive and disruptive.
- The space that I'm building in is very narrow - only just about wide enough for an infill terrace, which will be butted up against my wall on one side and my neighbour's wall on the other side, so no possibility of running drains under "clear air" - they'll have to go under a building. Which leads back to my original question of which house to run the existing house's drains under.
- I've thought of a third option (hybrid of options 1 & 2), which may be the most preferable, which is to run new private drains under each house, then join them together at the final man hole, with a shared connection into the main sewer in the street. That seems to be the most common way of doing shared drains.
- DLS says
Eventualy it is a property which will be sold. There is no point saving a few hundred pounds now to lose a few thousand on a sale.
Quite. This is the main reason I'm after some advice on it.
1. Are there any legal pitfalls or issues with shared drains when it comes to selling the house?
2. Would a solicitor usually flag shared drains as an issue to potential buyers? If so, how much of an issue? Just an FYI, or "I don't recommend that you buy this house"?
3. Who is responsible if my drain becomes blocked where it runs under a neighbour's land?
4. Has anyone here ever come across a situation (other than in flats) where someone's drains runs under a neighbour's building, rather than just under the neighbour's land?
Thanks again guys.