Downstairs toilet in extension and soil ventilation

[Alltheones]

Hi. I had a rear single story extension built I asked the builder to fit a waste pipe for a downstairs toilet.
from what I saw he cut a hole into the top of the clay pipe which was roughly 1.5m deep, around 4mt from my man hole and attached a collar with a 110mm plastic pipe straight up which has a adjustable bend on it ready for me to add to.
The toilet will be pretty much on top of this about 2m up from connection on clay with a shower and sink attached via a boss.
My question is venting my builder said I should add a durgo valve 1m above the bathroom floor, because this is a wetroom With floating toilet and sink I’m not keen on having this anywhere seen.
I can either take this into the boxing for the wall hung toilet but it would be boxed in so no ventilation above only below through floor boards and I’d never get to it again so not super sold on this
Or
Take it into the roof space up a false wall but it would be 9m away by the time I get there, but would be easier to access and have attic size ventilation.
I presume I can’t have a roof vent given mine and my neighbours windows would be 4mt away from it coming out of the tiles.
I could maybe take something outside as there’s a small gap between my extension and the neighbours.

I read sometimes no vent is required but don’t know the rule. Also does it have to be the 110mm size or can I go smaller.

 

[muggles]

What does your building inspector say? Both the extension and the new connection to the existing sewerage system are notifiable to Building Control, and your inspector will tell you what they want you to do

 

[Alltheones]

That’s not really what I’m asking.
I had a builder do the sewer and brick and roof so all that should have been checked, the job was handed to me as I’ll be doing the electrical work windows and gyp rock and first fixing the bathroom for future. So at this moment I’ve not had any contact with the inspector as none of that is done.
The inspector is there to make sure what I’ve done is right not tell me what he wants.

 

[Notch7]

Without images it's impossible to know what's going on.

To avoid internal boxing in, it's common to run the soil pipe up the wall outside and connect a toilet to it with via a hole through the wall. The AAV then goes on the outside pipe.

 

[muggles]

The inspector is there to make sure what I’ve done is right not tell me what he wants.

Believe me, it's much easier to ask them what they want to see before you start, than it is to persuade them that you've done it right when they have decided it's not. They can refuse to sign off until you make changes if it's not how they want it

 

[Alltheones]

Ye I get it but inspectors I’ve dealt with in my trade look at you like you’re a moron if you ask them how to do it.
I can upload some pics but not of the sewer as it’s underground.

 

[oldbutnotdead]

Check the Approved Docs- unless you've got dormer windows a roof vent should be doable. Don't like the sound of your connection to the clay though, if BCO hasn't already seen & approved it i'd be surprised if it'll get signed off

 

[Alltheones]

What’s wrong with the sewer attachment?

 

[JimCrow]

What’s wrong with the sewer attachment?

If they are picky this for a start,

 

[Hugh Jaleak]

The inspector is there to make sure what I’ve done is right not tell me what he wants.

There is your problem before we even start on anything else. The sewer connection should have been checked and approved by the BCO before it was buried, if you cannot satisfy him it's been done to regs, (and if he cant see it he wont know), then he could refuse to sign it off. If he then asks for a CCTV survey to inspect the connection and it's not done to regs, it'll have to come out again and be done properly.

Been to numerous bodged sewer connections where the Builder is long gone, and the first problem the householder finds is the WC backs up. BCO comes out and says works haven't been signed off, householder hasn't a leg to stand on and ends up footing the bill for remedials.

 

[muggles]

If they are picky this for a start,

View attachment 200461

This, and the fact that you're not generally allowed to have a junction outside a manhole.

Also, having your toilet waste falling that far down a vertical pipe straight into a horizontal will almost certainly cause it to go splat when it hits the horizontal and stick there. It'll block fairly quickly. It should enter the side of a pipe via a long-radius bend, preferably at 45° Y-juntion rather than 90° T-junction

 

[Alltheones]

I could be off with the depth to be honest as I never measured it, it could be about that.
All soil stacks vertical drop I’ve a big one down the inside of my house straight into a 90 bend?
The set up for the toilet downstairs it won’t be a straight drop I’ve got about half a meter horizontal to the toilet.

 

[Alltheones]

He must have seen it as he came out at dpc level and before that with the footings because I had to wait ages with Covid.

 

[muggles]

All soil stacks vertical drop I’ve a big one down the inside of my house straight into a 90 bend?
The set up for the toilet downstairs it won’t be a straight drop I’ve got about half a meter horizontal to the toilet.

The 90° bend at the bottom should be a long radius one, like this. A vertical drop into a tee cut in the top of a horizontal pipe won't provide the same smooth transition of waste from vertical to horizontal

The horizontal above ground in your setup is irrelevant. The issue is the vertical drop into the main sewer

 

[Alltheones]

Ye I know what you mean. I don’t think it has one of them given the distance the pipe upright is away from where I know the clay pipe was. I’m only really going off what he told me he did as he’d filled it in with dirt by the time I saw the pipe in, he might have angled it I don’t know.