Do I need 2 soil stacks?

[Susie]

My architect has put two SVP on the building regs drawing (already passed), one for the Ensuite on the South and one for the Shower room on the North wall.

I have recently discovered soil stacks are no longer put outside the build and can be inside with AAV.

I'm looking for advice on what's is best.

The garden and main space is to the South of the build if I can avoid an outside soil stack that would be great.

The ensuite has a vaulted ceiling though so no space for AAV to vent into without (option 1) creating a false ceiling, or (option 2) boxing the stack in but allowing for air to enter when AAV needs it. or (option 3) moving the stack into the plant room which has a lower ceiling for access to MVHR pipe runs etc but I don't want to swap the toilet with the sink, or (option 4) plumbing under slab straight across to the North side where the shower room toilet is and just having one stack on the outside wall.

Is it a possible to have pipes buried in the slab, apx whole width of home 8.3m? Is it a risk in anyway?

It would also remove a 12m stretch of external soil pipe in the ground on the south side, saving in cost of pipe but not trench as rainwater to soakaway still in same area.

Nothing is started yet so anything can change at the moment.

 

 

[joe90]

Yes, IMO external stack pipes are a no no for a modern build (if possible), they look rubbish and create cold bridges. The only thing you have to bear in mind is soundproofing any boxing in as you don’t want to hear it when having your dinner 🤷‍♂️. Pipes In or under slabs are ok as long as rodding access is provided.

[Susie]

@joe90 is that rodding access in the house or outside at the chambers. 

[joe90]

1 hour ago, Susie said:

@joe90 is that rodding access in the house or outside at the chambers. 

Wherever but outside is better as you don’t want rodding eyes in the house .

[Iceverge]

You may need a stack of you're on a private septic tank. Ours is on the back of the garage with an AAV inside. 

 

I think if you're mains then one per street is ok. I stand to be corrected mind you. 

 

 

[Susie]

I’m thinking of linking the soil pipe for the en-suite under and across to the North side and joining the inspection chamber there, where the plans show an inspection chamber on the south side that could now be a rodding point .

 

@Iceverge we’re not on a septic tank we will join the main sewer as it passes through our field.  Interestingly the sewer was created in the 70’s for the school higher up but I only just found our that some of our neighbors below school but higher than us are not connected to it and are on a septic tank, they in turn didn’t know we were on the main sewer. Our new build will be directly connected so we fall in the 1-4 houses that means every third house has to have a external SVP as we are only 1 house I have read both that we should have a SVP and that we can just have AAV so have decided that one pipe on a rear wall I will hardly ever stop and look at doesn’t matter much.  I’m sure it’s been mentioned on here but it’s also come up in my own browsing research, that the cold bridge is not a big problem I’ve also read that condensation on boxed in internal pipes can also be a slight problem.

 

 

[Iceverge]

Having stressed over this lots a soil pipe it turns out is only a minor thermal bridge. Either internally or internally. 

 

There is an argument for having it outside too. Far more accessible in the event of blockage etc. I seem to remember one of the senior statesmen @tonyshouse prefers it. 

 

In my mind that plan for the ensuite will work. I'm not the most experienced though.