soil stack question

[jmgh]

Hi,

I have no soil stack on the outside of my house. The waste from the existing toilet (on the ground floor) goes straight down into the concrete subfloor behind the loo. kitchen and sink wastes go into a gully.

I have built a new extension en-suite directly above this toilet, and I'm wondering about waste from the bath/sink/toilet in this room.

can i move the existing ground floor loo forward, run a soil pipe vertically up from the existing soil in the concrete floor through the wall cavity, and then tee the ground floor toilet and the upstairs toilet and other wastes into this?

Could this soil pipe then vent into the roof cavity with an AAV on its end, or would it have to vent outside? I'd rather not vent outside with an open end as if it must be 1m above windows it'll end up about 3m above this part of the roof as I've got veluxes in the roof!

Finally, can anyone tell me if its ok to have bends in the soil stack? Ideally I'd run it to the corner of the building before continuing vertically up through the house.

Many thanks in advance for any advice/opinions!

j

 

[Hugh Jaleak]

A diagram would be useful, but before you do anything else, be aware bends are frowned upon in the wet section of a stack, and also depending on distance between the connection of the downstairs WC pan and the bend where the existing drain goes from vertical to horizontal will govern if it'll work, let alone be allowed.

An AAV should be ok as I assume the drain is vented elsewhere, this being currently a ground floor WC connection.

What is the B.C.O.'s take on the drainage arrangements? Unsure as to how you've built an en suite without plans already in place for drainage.....

 

[jmgh]

Thanks Hugh,

I will talk to my BCO next week about this on his next site visit. Just wanted to be armed with what is and isn't possible…

The drainage situation is a bit unusual I realise, but then so is my build! It took a whole lot of investigation and demolition to find out what was what, and the project had to move forward at the same time.

j

 

[Hugh Jaleak]

Fair enough, be aware bends are best avoided in the wet section (for various reasons), usually a long radius bend is required at the foot of a stack, and you need to be careful with regard to compression, (when the upstairs WC is flushed, the contents of the flush doesn't cause disturbance in the WC below.)

If a dedicated stack for the upstairs can be provided with an independent connection to the drain at a suitable point then this would be preferable IMHO.

 

[ALCPlumbing]

Your main stack must be able to not only pull air in but allow air out. This is to provide an equilibrium of pressure within the system.
If you only have the one stack then strictly speaking it shouldn't have an air admittance valve on it. If yo have more than one, it is the stack furthest from main drain in street that must be able to vent both in and out.

 

[treerat]

It would be best to put a new stack in outside the house that would go streat up witb an air admitance valve on the top under the soffit
Any bends in the stack the way you have sagested to do it is not the don thing. They would have to be long radius bends with access for cleaning as solids could stick to the pipe on the bends and cause a blockage
Check your plans as they should have a section no wast water if they have gone through building regs.

 

[ALCPlumbing]

Your main stack must be able to not only pull air in but allow air out. This is to provide an equilibrium of pressure within the system.
If you only have the one stack then strictly speaking it shouldn't have an air admittance valve on it. If yo have more than one, it is the stack furthest from main drain in street that must be able to vent both in and out.

 

[jmgh]

Thanks for all your help.

As usual there is no simple answer! I'll chat to the BCO this week and see what he recommends.