Adding a soil stack internally - is this practicable

[freeonboard]

Son just moved into his first house (a renovation project if ever there was one) & he wants to add an en-suite shower, basin & w.c. to the first floor bedroom. - It so happens that directly underneath in the garage area/utility there is a toilet room with a w.c. that flushes directly into the underground drainage.
I wondered if it was feasible/sensible/allowable to build an internal soil stack that could service the new en suite and this existing toilet. To do so would require that the wet section would be installed in the corner of the ground floor room and have a couple of 45 degree bends at the bottom to then run approximately 1 metre horizontally. This horizontal section would then enter the existing toilet drain point with the toilet itself joining into the new horizontal section.

Do you guys think this idea is possible? I understand Building Control would have to be involved but at this planning stage I want to help him understand what is and is not feasible.

Thanks in advance for any advice you can offer!

 

[John D v2.0]

Sounds fine, due to the height it would need an aav at the top to prevent traps being sucked. 2x 45 bends is fine at the base of the stack, just support correctly.

 

[freeonboard]

That was quick! Thank you John, much appreciated.

 

[Newboy]

Rest bend at the base of the stack rather than 45s

Building control will not be happy if the new junction is a blind connection/lateral

 

[John D v2.0]

Good point about the blind junction - basically all parts of the system must be clearable according to building regs (not to mention common sense) so you'll either need a rodding point at the junction, or from branches.

re the rest bend, 2x 45s is just as good as a long radius bend, but a rest bend is cheaper.

 

[Nige F]

To do so would require that the wet section would be installed in the corner of the ground floor room and have a couple of 45 degree bends at the bottom to then run approximately 1 metre horizontally. This horizontal section would then enter the existing toilet drain point with the toilet itself joining into the new horizontal section.

Do you guys think this idea is possible? I understand Building Control would have to be involved but at this planning stage I want to help him understand what is and is not feasible.

!

Possible but not best practice with that horizontal run and the wc connecting into it then dropping into an existing drain inside building. Pretty sure BC won't pass it . Can you post a drawing including what's outside - assuming the room has an outside wall

 

[freeonboard]

Thanks everyone for the replies... food for thought! Re outside there is a guttering downpipe that disappears into the concrete walkway but I've no idea what it drains into. (I'm 100+ miles away from his place so can't check it at the moment.)
I guess I shall have to have him talk to BC to get an idea of whether they will accept this or not assuming sufficient rodding points. If the answer is no then we will have to bite the bullet & assess what's needed for a normal, vertical, exterior stack.

Thanks, all!

 

[Newboy]

re the rest bend, 2x 45s is just as good as a long radius bend

Although it the same change in angle, the long radius of a rest bend is specifically designed to change the flow in a long, slow & smooth bend - that's why there is a rest bend as opposed to a short radius 90° (or 2 no. 45°)

In addition, the restbend has a support function hence the built-in 'foot'

 

[John D v2.0]

Although it the same change in angle, the long radius of a rest bend is specifically designed to change the flow in a long, slow & smooth bend - that's why there is a rest bend as opposed to a short radius 90° (or 2 no. 45°)

In addition, the restbend has a support function hence the built-in 'foot'

Thanks for the reply. Support is indeed a very important thing.

standard 90 is a world of difference to two 45s. With 45s you can make a larger than 200mm radius within reason.
Rest bend is purpose made for the task no doubt there.
My source is Marley's design guide it seems to be an excellent resource and recommends 45s in certain situations. I've used a pair myself and it seems to work well although only a two storey stack.
http://www.marleyplumbinganddrainag...p/design-advice/soil-and-waste-design-advice/

 

[Hugh Jaleak]

The Rest bend is designed to allow the waste to 'flow' round from the stack into the drain, and avoid compression of the air under the waste in the drain. The waste is dropping vertically from a fair height at speed, if you've ever seen the mess in a chamber that's close to the foot of a stack, especially where a rest bend hasn't been used, you'd know why they are important! This is also the reason connections are not allowed within 450mm of the base of a stack.

Freeonboard, I am with Nige here, the BCO is (in my mind) unlikely to allow your proposal as described. Bends are frowned upon in the wet section of a stack, and there will also be an issue with noise, when discharge from above hits the bend at the base of the stack on the ground floor. I suspect you'll need to excavate and route a new drain as required to accept an external stack. Ultimately the Building Regs are you guide and the BCO will be looking for compliance with those. https://www.planningportal.co.uk/in...ments/71/part_h_-_drainage_and_waste_disposal