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Groundwork & Foundations

Moving thames water manhole

I have dug out the foundations for my extension. I want to know how I go about removing the old man hole and fitting a new one. From the drawing I’ve been told to fit a Y-junction and remove old manhole. What’s confusing is does the water from the neighbours need to flow in to the new inspection chamber ?

3 Answers from MyBuilder Groundworkers

Best Answer

Moving a manhole requires approval on a Building notice, also a build over agreement with Thames Water.
If your drawings are from a structural engineer and he has indicated just a "Y" branch this would suggest this will just be a rodding access from the new chamber. You would then replace the existing open gully's with a new sealed pipe. Talk to your building inspector and he/she will advise you.
If in doubt get a professional in, get this wrong and it will cost you.


Answered 4th Jun 2019

Just to simplify things a bit for you if the manhole you wish to move serves only your property what the y is doing is joining the common sewer pipe and providing you with a branch to which you can connect to.
Your new drainage pipes should have adequate falls to your new manhole and from the manhole you should have adequate fall back to your branch position.
A Thames water build over notice is only applicable if Thames water already hold the information on your manhole (often this is not the case) so it will be building control that will update the information as part of sign off.
The drawings that you have would have gone through the planning process even under permitted development but if in doubt your building control officer will set you straight.
Good luck with your project.


Answered 3rd Jul 2019

The drawing for your extension should have been approved by the local authorities. If that’s the case, you should follow it to the letter, that way you can’t go wrong and you’ll keep the the building inspector happy.
I suspect the y junction is to pick up the foul water from the extension.
The only thing I would suggest if it’s not clear from the drawing, is to use same size y junction and new pipe as the existing.


Answered 27th Jun 2019

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