2 WC's on 1 soil pipe branch?

[KevinManc]

Hi

I'm about to put in a new en-suite bathroom in a loft room. I need to connect the WC to the waste system.

There is another en-suite directly below and the waste pipe for it passes into a boxed in void and out through the wall to a vented soil stack. I would like to bring the waste branch from the loft down into this void then connect it to the existing waste branch, via a swept T joint. I would put an AAV in to loft (the house has a second vented stack at the rear). doing it this way would not require me to extend the exterior stack and make a hole to take the loft waste branch out through. I currently have the void open and would find it easier to access and make joints there than outside. I'm not sure I can do this. The regulations don't say it can't be done, and does acknowledge that multiple appliances can be on one branch, but only illustrates basins being on the same branch as a toilet.

Can anyone see a problem with what I am proposing? (View diagram in my albums)

 

[plummerman]

i presume you mean to take preposed new branch veritcally upwards from your exsisting internally stack? I:E' creating an l shape. If so, first problem you will come across is the free fall effect the waste will create due to the drop. Blocking will occur quite rapidly, on the same line also the regs say all change's of direction require the area to be accesible for inspection. (rodding eyes) if this in a void how would you reach it. lastly all alterrations have to be approved by buliding inspector on new or altered soil and waste systems.

 

[Softus]

I don't see a technical problem, but are you aware that the work you're proposing needs LABC notification and approval?

 

[KevinManc]

Yes I was thinking of dropping the branch vertically towards the branch below but hoping to find a swept T to join the 2 thus preventing a straight drop and splat. I don't know if you can get such a joint yet. I would have put a rodding eye at the top of the drop and maybe inside the void. There is also the possibility of having a rodding eye on the boss of the outside stack.
The void has an access panel on it.
I've never heard of LABC notification - what's that? The Building Control Officer is involved in a Regularisation of the loft room and will be inpecting most of the work but I haven't notified him specifically of the waste stack work.

 

[Softus]

If the BCO is already involved (or about to be) then you've already fulfilled your notification duty.

The nearest thing to the swept tee, that you're so laudibly designing in, would be the following:

(Imagine it laid on its side, of course, i.e. with the branch pointing up.)

 

[Richard C]

Maybe I’ve misunderstood your plans for the vent but the way you’ve shown it the new facility is higher than the existing vent & you cant do it like that that! The vent or AAV has to be above the highest point of overflow (the new sink in your case) for obvious reasons!

Other problem is the regs. won’t allow you to drop one lot of poo onto another lot of poo that could potentially be lying in a horizontal branch as it will inevitably cause a blockage. Manifold systems are used in communal toilets but these have only a very limited drop (around 130mm) into the manifold invert; yours is much higher than that. To accommodate large differences in the height of drain inverts, it’s also permitted in manholes by means of a backdrop, either constructed internally or externally but the discharge must be at 45 degrees to the main flow &, more importantly, entering at the side & not from the top; so, again, only limited drop. If you Google Hunter or Marley waste systems they have very useful design guides which are far more informative than the Part H regs. you may find something in there but I think you really are going to have to discuss your proposals with Building Control. You will also have to notify them of your proposals, they will almost certainly want to inspect it & may want it tested; & if they don’t already know about the en-suite they will also be very interested in what you’ve done by way of ventilation in the en-suite but soundproofing stud walls may not be a problem if you’ve no other rooms up there.