running waste pipes into new soil pipe

[antsbradley]

Hi,

Just building an extension, including a shower / WC room on the ground floor.

The builder that I had in to build the shell has run a new 110mm soil pipe from the IC in under the joists and up to where the new WC pan will go. However I need to also connect the 32mm and 40mm wastes for the basin and shower. As the shower drain will be at / below floor level it will have to join into the waste under floor level (suspended floor), and I suspect the basin waste will also have to join below floor level as there wont be much of the soil pipe left above the floor before it joins the pan.

I know that making connections under a then to be sealed down floor is not ideal, so whats the best way of making those connections? I was thinking of a strap boss for each, stacked one above the other to prevent cross contamination, but am concerned that the rubber seals will fail over time. I guess the only other option is a boss pipe inserted into the rising soil pipe, at least I could then glue the connections together.

How would you do it?

Many thanks!

Anthony

 

[Richard C]

I’ve used solvent weld boss straps onto a soil stack in my new en-suite which sounds like a similar situation to yours except mine is on the first floor. I wouldn’t worry about the rubber seals, they will almost certainly outlast you; or you could use a boss pipe if you can get one in! You will need to vent the main soil pipe or you’ll be continually drawing the shower & basin traps when you flush the loo or the loo trap when you use the shower. You can do this using either anti-siphon traps or valves fitted in the waste runs or a vented stack on the main soil pipe. This can be either open to atmosphere through the roof or a concealed stub stack with an AAV (Durgo valve) fitted as I have; your BCI will probably insist on there being at least one open vent somewhere else on the system though. The stub stack has to be higher than the highest overflow point on that run for obvious reasons.

I’ve found this is a very useful guide which also incorporates the Building Regs. requirements;

http://www.hunterplastics.co.uk/pdf/soilandwaste/swt_brochure.pdf

I keep banging on about it but I assume you do have a building notice running with your LABC for inspection of the extension & service connections & that they have inspected the new foul drain run & it’s connection into the existing system? Sometimes they insist on a water or pressure test as well.

 

[antsbradley]

Hi, thanks for the detailed reply, I hadnt thought about the vacum so will have to look into the best way of venting, I dont really want to raise the soil pipe up higher than the basin, so will look at the other methods you also suggest.

I think I can get a compact boss pipe in there, and at least then I can solvent weld everything which I feel a bit better about than rubber seals (prob an irrational concern), but does it matter that both wastes then come in at the same level?

Yes the whole project is under the watchful eye of LABC and they are happy with the new soil pipe and IC so far. I actually asked the inspecter about it on his last visit, but he didnt seem very interested in the waste/soil configuration, or how any of it was done.

Mant thanks,

Anthony