Underground soil pipe

[Wolverhampton123]

Advice Request: Underground Soil Pipe Running Along The complete Length Of The Footings.


I’m planning a side extension to my property. The full length of the proposed footing will run in line with an existing 150mm vitrified clay (VC) underground soil pipe, which is approximately 1.5m deep and connects to a shared drain.


The ground floor of the extension will be a carport, so there will be no concrete slab—just gravel.


My question is: Can I leave the existing drains in place (as it will not be within the footings) and install two inspection chambers approximately 500mm to the side of the existing manholes. I plan to reroute the new soil pipe 500mm from the footings, and then reconnect it to the main drain.

I have attached some drawings (drain locations) and photos of the existing. I do love a challenge.

Thanks in advance.

Just added a new image with the existing manholes not shown on the Severn Trent plans

 

[foxhole]

Contact water company for build over agreement .
When I did my rear extension we removed our inspection chamber and connected right thru to interceptor then put our own inspection chamber outside the build line.
(Thames water insisted original stayed in clay pipe .)

 

[Wolverhampton123]

Thanks for the quick replay Foxhole,I'm just trying to get my head around this.

I’ve sketched out the layout:
• Blue = existing manhole and clay pipe
• Red = proposed inspection chamber and new run
• Yellow = the extension


The existing manholes are 1.5 m deep and do not need to be relocated. Will this arrangement work?

 

[stevie888]

Looking at your original drawing,the simplest solution is for the top chamber to be relocated towards your property. I assume its a 6" pipe coming in from the right?

At the front, drop your new chamber in over the existing connection. The short length of pipe across to the existing chamber will need to be increased to 6" and the channel modified.

You should have enough fall to make it work but it might be worth checking.

This is a perfectly valid engineering solution and Thames should be fine but you won't know for sure until you ask.

FWIW if you had Anglian this would not be a simple buildover though as you will be altering their pipes and I doubt if Thames will be different

 

[Wolverhampton123]

Thanks for the reply, Stevie. Yes, it looks like it’s 150mm – the engineering concept seems straightforward. I just wish there were more detailed resources online. Most of the YouTube examples only show minor bridging where the footings cross through a small section, without much explanation of what's considered acceptable.

Stevie – big ask, but would you be able to highlight your recommendation on my sketch?

Also, a big thank you to everyone who helped with my last self-build rear extension – the results were fantastic!

 

[Wolverhampton123]

Really getting into this now—my mate just sent this over (carpenter). Just another idea: since the carport is staying and has gravel, this might actually work?"

 

[Murdochcat]

Best you talk to your water company. They decide what you can and can’t do

 

[Wolverhampton123]

Thanks Murdochcar-I'm just trying to get a feel for things before they start making suggestions. I want to go in with some ideas and knowledge, and the help from you all really goes a long way.

Just to note, The input I received from my last build here was brought up with the building surveyor, and he seemed impressed with some of the alternative solutions. Just goes to show these forums are well worth it.