Moving manhole for extension?

[HotChoc10]

I'm musing about getting a side infill on my terraced house, but unfortunately there's a manhole in the way. I've had a look at the Thames Water website and seen that you can apply to move this as part of the works - you can no longer build over them.

Has anyone successfully done this and got an idea of how onerous the approval process is, how much £ it will add to the build, and whether the plans for moving it would be a job for an architect or some kind of specific drain person...? You can probably tell I'm pretty clueless!

I haven't done it but had extensions plans and planning permission then decided to move. Our builders were going to just move the access point further down the pipe and they didn't think it was an issue at all. Good luck with it

I looked at it for a previous house. Think it was possible, but expensive.

We moved into a new build and there was a manhole in the middle of the garden that hadn’t been on the plans. We complained and a team came round and moved it (to the garden of the next house along that wasn’t sold yet!), took a few hours.

I had a manhole and a drain moved as part of an extension. It took a lot longer than I expected and was expensive ☹️

Would you be comfortable saying how much @c0nnie? I reckon if it's much more than about 5k it might not be worth it.

Be careful - you don't want to build over a sewer. the rats will come up an enter your property. shudder. Check if it is a water pipe or a waste pipe, and think very carefully if it is the latter.

I'm in the house with the X on it. The red lines indicate foul sewers so I would assume the manhole links the pipes from my house to that...?

It'll be the lateral sewer that takes wastewater (toilet, sinks, bath, washing machine) from your property to the main sewer. If it only serves your house then you are responsible for that pipe until it reaches the boundary of the property. In my 20+ years in the industry I have never heard of rats coming up into houses!! The reason they don't want you building over it is because if it blocks you'll have no access to unblock it, or if the sewer downstream block it will backup and surcharge into your extension. You'll probably need to get a dye test and survey done. if it's to the side of your property it might also serve the property next door? I'd guess the manhole is on a right angled bend to turn down the side of the house? In which case you could probably move it to the back garden but there's more of a risk of blockages on bends so you'd need to be very careful not to flush anything you shouldn't. I'm afraid I have no idea of costs.

Thank you @emmathedilemma that's really helpful info!

Ours was a sewer as @emmathedilemma describes and it also served our next door neighbours.

It cost about £7k and that’s a few years ago. It took about two weeks because we were still living in the house so they couldn’t leave it disconnected overnight.

Looking back, I think a lot of time was wasted by the contractors. It would have been cheaper to put us and our neighbours in a hotel and done the job faster.

You could remove and re-locate it onto the line of the existing run. Any manhole on the public/shared sewer would need to be to adoptable standards. Thames Water would usually want to CCTV the sewer, before and after the works too.

Your other option could be to remove the manhole completely (which is what Thames Water would state anyway) and provide a new inspection chamber or manhole to the side of the existing sewer. You’d then form a new “Y” connection at the base. This nee manhole/chamber would not need to be to adoptable standards.

A standard Build Over Agreement with Thames Water is £299 if applied for online. You’d need drawings of the sewer to accompany the application, which you may be able to do yourself or instruct a professional. The latter obviously incurring additional costs. Or you can try their self-certification scheme, which will save you all those fees. Depending on the information you can provide will determine whether a formal BOA application would be required.

@Changethetoner, They must be clever rats if they could open a manhole cover even if it was built over.

We had a rat appear in an upstairs toilet pan. We have no idea how it got there! We have the pipes and drains checked with cctv and nothing was broken. We wondered if it climbed in through the open window which leads to a section of flat roof. My elderly mum discovered it! So no, they don’t lift manhole covers but they are very resourceful when they need water.

@devildamo - thank you, that's really helpful

We have the same problem - annoyingly the manhole only just overlaps the line of our planned side return extension - and have been quoted about £1800 for the work, not including permissions from Thames Water.

I’d think a rat could find water easy enough without having to climb onto a flat roof then through a window just to drink out of your toilet 🤣 what would it have done if the seat was down ? Headed for the fridge ? 😆

£1800 doesn't sound too bad @zinnia! What trade is it you need to move it, or just the same builders as for your extension?

@HotChoc10 yes that was from my builder. Was a bit of a back-of-the-envelope cost though as not got a proper quote in yet. Just as a caveat!

@Chumleymouse

I’d think a rat could find water easy enough without having to climb onto a flat roof then through a window just to drink out of your toilet 🤣 what would it have done if the seat was down ? Headed for the fridge ? 😆

😂😂😂 @Chumleymouse