Clay sewer running through footings

[c0wb0y]

Hi folks,

So I'm about to embark on a full-width (approx 6.5m) rear extension to span the back of our semi. There's a shared clay sewer (approx 8~9" in diameter) that runs perpendicular to our proposed footings. The sewer serves me and the neighbour but I won't have a need for it once the extension is built as I'll tap into the run further down. The sewer is approx 2ft deep and terminates in a brick-built chamber. From there, the waste goes off towards the main road.

I'm aware of the usual 'lintel over' method and will be seeking a 'build-over' agreement from Severn Trent. They give 2 options: provide a CCTV report or replace it with plastic. I'm opting for the latter but here's the questions:

1) The clay sewer is approx 8~9" in diameter. Every builder I've spoken to has said to reduce it down to 6" plastic using those Jubilee Clip rubber couplers - does this sound right?

2) Is it ok to 'couple' the clay to plastic in the 'linteled over' section of my footings? I guess what I'm asking is how far along should I cut the clay? I'd love to bury the joint (coupler) in the neighbours garden but they won't allow me so it'll have to sit in my footings. Will that be an issue?

3) The span of my extension is 6.4m. That means I need to buy 3 x 3m lengths. Is it OK to have a similar coupler buried underneath my kitchen slab?

4) Am I wasting my time: why fix it if it ain't broke right? Should I opt for the CCTV report option instead?

 

[jeds]

Difficult to follow. I'm not sure of you are saying the line you propose reducing is a branch to your property or continues on to the neighbour? Why would just 2 properties have a 9" sewer? If it just serves your property and will become redundant - I'd reduce it down to 4".

A sketch might be easier to follow.

 

[c0wb0y]

Difficult to follow. I'm not sure of you are saying the line you propose reducing is a branch to your property or continues on to the neighbour? Why would just 2 properties have a 9" sewer? If it just serves your property and will become redundant - I'd reduce it down to 4".

A sketch might be easier to follow.

 

[jeds]

Ok, I don't see it being feasible to reduce the line to 6" without doing the whole thing into your neighbours garden, and I wouldn't have thought Severn Trent would be happy with that either - but you'll have to agree that with them. Personally I would have it surveyed and as long as everything's tickety-boo, I'd leave alone.

 

[Ian H]

Is it 8 or 9” on the outside?

I bet it’s 6” really.

 

[noseall]

Is it 8 or 9” on the outside?

I bet it’s 6” really.

Ditto.

 

[Hugh Jaleak]

Never reduce a Sewer down, all you do is introduce a pinch point for solids and it'll block very quickly....

 

[Laggy]

I dealt with Severn Trent for my build over agreement. Why don’t you just do the CCTV survey and forget all the faffing. Mine cost £165 from a bloke with a giant poo emoji on his van.

Is the pipe covered in any concrete? Mine was, and as a result building control were happy with me just laying some mesh over the top of it before pouring my footings over it.

 

[JJM1987]

If it’s on the public sewer maps I doubt the sewer providers will let you replace in plastic it would need to be VC, that manhole would need to be 500mm plus away from your footings too. Strange it’s 9inch, as said above probably a 6er just encased