Cost of moving a drain?

[LongTailedWinterBird]

Hi, has anyone been through the joy of moving a drain? We've got planning permission for the world's smallest extension and are now thinking of going bigger...but the new foundations would hit an existing drain. Our budget is painfully tight so we'd have to cut corners elsewhere in the build, and I'm looking for any insight as to how much cash I need to try and claw back to afford the drain move! Thanks in advance.

Depends! Is it your drain only or does next door to through it? If it's yours only and there's enough height difference on the pipe you can do what you like and it will be hundreds, although you'd need it inspected as part of the overral work.
If it's a neighbor's drain too you'd need to send drawings and several hundred pounds to the water company and they will possibly approve and ask you to put in enough access covers or rodding points. The required level slope will be harder to get and this will be a thousand plus.

Hi @johnd2, thanks for your response. The drain in question flows from our house to our immediate neighbour, then out to the street. We had a CCTV survey when we were thinking of building next to it (rather than over it), and my impression is that it will be a complete faff to build over! So it sounds like we're in the £1k+ territory, sigh.

Sounds like your drain only then so you can move it without water company approval, only building regs which your would already be paying for with the extension.
All you need to do is make sure there are no internal drain covers, and all sections of drain are clearable with rods or jets. You might be able to get away with leaving the pipe and adding rodding points, but more likely a bit of a reroute but your designer should be able to come up with something workable.

Thanks @johnd2, that's helpful.