New soil pipe depth

[Action Joe]

Hi,
I've been reading this forum for a while, but I'm only now braving my first post. I was hoping someone may be able to advise?

I'm building an ensuite in my master bedroom which warrants a new soil stack on the side of my house - the existing stack is on the other side of the house and isn't really feasible to connect to. My house uses a combined surface water / foul water sewer. The manhole cover is out the front of my house and is shared by my neighbouring 2 properties. Consequently a soil pipe cut across my front garden to my neighbours and happens tee off to serve my down pipe on the front corner of the house. This is the underground pipe I was planning to tap into. I would be running approximately 3m of pipe to a new soil stack, that would then service the ensuite.

The issue I think I'm facing is that the underground pipe directly connecting to the existing down pipe is only 18cm below the surface. When installing the new soil stack 3m away including a fall of 1/80 (3.75cm), I don't think there will be enough depth (18 - 3.75 = 14.25) to install a rest bend under ground. Some of it would protrude above ground.

My questions are:

• Do I have to use a rest bend? or can I use something else more shallow/shorter? A normal 92.5 deg bend?
• Is the drain so close to the surface allowable? If so, do I have to cover it with something?
• Are there any other options to connect to this underground pipe (bearing in mind the new soil stack is planned to be situated next to an external chimney breast making it difficult to move the soil stack closer to the existing pipe)

Underground pipe will be brown PVC.

I've read over the building regs about drains and can't really work out these things.
https://assets.publishing.service.g...achment_data/file/442889/BR_PDF_AD_H_2015.pdf

Any help would be great!

 

[Ian H]

Old clay rest bends are much tighter than the modern plastic ones. Not sure in regs but I would happily use a normal 90degree bend.

If you use a single socket one you could have a black socket on the plain end to come out of the ground.

Bed it on pea gravel and cover with whatever you want.

 

[Ian H]

For example:

 

[Leofric]

Bed it on pea gravel and cover with whatever you want.

Doesn't it depend on the depth of cover

 

[Ian H]

Doesn't it depend on the depth of cover

Yes but you could cut a block paver in half if it’s only an inch deep.

 

[Leofric]

Yes but you could cut a block paver in half if it’s only an inch deep.

how near the surface are you saying a drain pipe can be

 

[John D v2.0]

Could just build up the surface a bit, if it's a lawn it would be more acceptable than a drive.

 

[Ian H]

how near the surface are you saying a drain pipe can be

Sometimes it’s where it can be rather than where it should be.

 

[Leofric]

Sometimes it’s where it can be rather than where it should be.

So what minimum cover should Action Joe try and achieve

 

[Ian H]

So what minimum cover should Action Joe try and achieve

As much as he can while maintaining a decent fall.

 

[Action Joe]

Thanks for the comments. Being new on hear I was expecting to be notified of responses, and I think I got one, but not for each. Sorry for my late reply!

I've actually spoken to my local building control and they have told me I must have a rest bend at the bottom of a new soil stack, even if it protrudes above the ground! I'm not sure if this really is true as I can't see it written anywhere. If I speak to another building control, I may get another answer... A bit frustrating for me, but it is on the side of the house no one sees. I think if I was allowed a normal 90/92.5 degree bend I would be just OK with raising the ground slightly. Will see what building control say when I finally get it in. I'm hoping it is this week!

 

[^woody^]

I can't see it written anywhere

Have you checked BS EN 752?

Or the guidelines of every single drain pipe manufacturer?

 

[Leofric]

Why would you think you would get a different answer from another building control As your local building control appears to be giving you advice you could ask them about cover to drains near the surface and what precautions to take; for example NHBC recommend covering pipes in gardens with a paving slab with a minimum of 75mm pea gravel between the underside of the slab and top of pipe (and soil over the slabs) where drains are not at the minimum recommended depths.
'I've actually spoken to my local building control and they have told me I must have a rest bend at the bottom of a new soil stack, even if it protrudes above the ground! I'm not sure if this really is true as I can't see it written anywhere.'

 

[noseall]

We have had the unfortunate situation where a rest bend is visible above the ground. Not pretty. You can build a plinth around it or paint it black or whatever,

BC ask for (not demand) 300mm cover. Often this is impossible and accepted. Fall on the drains and common sense supersedes the unreasonable.

 

[noseall]

Sometimes it’s where it can be rather than where it should be.

Correct.