2 toilets 1 branch HELP

[Diditmyself1]

Hi all.

Im currently trying to improve my shower room to create a more useful en suite. I have enlarged the room so it is big enough to add a toilet to the room. I will shortly need to connect the new toilet to the soil stack.

The only way i can see this being possible is to use the existing waste pipe of the toilet in the bathroom and service both toilets from the 1 waste branch.

To do this i will need to lengthen the existing waste by about 70cm and connect to new toilet.

I assume that this is not ideal practise but cannot find any regs to prohibit connecting 2 into 1.

Any advise is much appreciated as to whether this is acceptable/workable.

On the photos (from below) the new toilets location will roughly be where the white board is.

View media item 101830View media item 101829View media item 101828
Thanks

 

[John D v2.0]

Should be fine as long as the flow won't go from one to the other. The fall would need to be correct too towards the stack.
Might be tricky to get past the herringbone strutting without destroying it though, not that that stopped the previous plumber by the looks. You can always go above floor level and box it in as a last resort.

 

[Hugh Jaleak]

Move the herringbone to far side of proposed new WC position, fit a junction where the existing bend is and then carry on to connect your new WC.

When doing the work I would be looking though to cut through the existing 110mm pipe and fit a coupler, continuing on from there with new pipe and fittings. (Probably just before the 1st socket on the horizontal run, replace from there.) Attempting to dismantle an existing joint and then expecting it to seal again may be asking too much.

 

[Diditmyself1]

Thanks for your responses.

Do you think i will need to add a vent pipe on the new toilet to prevent siphoning when old toilet is flushed?
Had thought about running 40mm pipe from boss on new toilet pan connector up into the loft and fit with aav. Then box in pipe.

Do you feel that is necessary? Would rather not do it but obviously prefer a bit of ugly boxing to a ugly smell.

Thanks again.

 

[John D v2.0]

As long sa the branch gradient is flat enough you won't have trouble with syphoning. But you can fit an aav rather than needing ventilation if you have an existing vent pipe on the system anyway, then it wouldn't need a full boxing in column.

 

[Diditmyself1]

Thanks john. At the moment the only vent on the system i can see is 40or50mm pipe that comes off the soil stack at first floor level.

At some point in time i think previous owners did away with 110mm vent pipe exiting top of stack out of the roof. The remainder of the stack now stops just below my bath.

 

[John D v2.0]

That vent doesn't really comply as 50mm isn't big enough for the soil stack. But you'd probably be ok, especially with an aav on the system. The other issue is it should be 900mm or so above any opening windows within 3m horizontally. There may possibly be an aav on top which means there's no positive pressure relief so if the drains surcharge it will bubble up your loos etc and also you aren't supposed to use aav outside.
So either way it's not quite right, but you'll probably get away with it.

 

[Nige F]

That vent doesn't really comply as 50mm isn't big enough for the soil stack. But you'd probably be ok, especially with an aav on the system. The other issue is it should be 900mm or so above any opening windows within 3m horizontally. There may possibly be an aav on top which means there's no positive pressure relief so if the drains surcharge it will bubble up your loos etc and also you aren't supposed to use aav outside.
So either way it's not quite right, but you'll probably get away with it.

You're right John, that's a small aav for waste pipes. Personally I would run 110mm instead of the waste pipe, up + over the gutter to vent - if possible to do this - that should ensure the 2 toilets are OK

 

[Nige F]

Thanks john. At the moment the only vent on the system i can see is 40or50mm pipe that comes off the soil stack at first floor level.

At some point in time i think previous owners did away with 110mm vent pipe exiting top of stack out of the roof. The remainder of the stack now stops just below my bath.

Is there enough room under the bath to exit the wall ?

 

[Diditmyself1]

Thank guys for your input. Regarding the current vent i was aware that its location and size dont meet building regs, but it has seemed to operate fine for a number of years and the short time ive been here, so unless building control flag it up id prefer to leave that job alone and add a aav off the new toilets connector. There is not much room under the bath to add a 110 vent, which is the best solution, only wish it had been done properly at time of previous alterations.

 

[John D v2.0]

Building control would be most interested in things becoming less compliant than before, anything old that hasn't changed should be outside their interest. However you'll just have to wait and see and deal with that if it happens.

 

[Hugh Jaleak]

Could you get an 82mm pipe under there? Reducing to 3" (82mm) for the vented section is allowed.

 

[Diditmyself1]

Im not sure i could make any alterations really without removing bath.

And even then i dont think i'd have the height for a larger diameter pipe. The existing one is already close to underside of the bath. I suspect previous installer would have put in right size vent had it been possible. I'll need to have another think about alternate solutions otherwise i'll just go for the aav off the new toilet idea provided thats sufficient.

 

[Hugh Jaleak]

You said you think the previous owners had done away with the vent going out the roof, is that route still available?

 

[Nige F]

Im not sure i could make any alterations really without removing bath.
And even then i dont think i'd have the height for a larger diameter pipe. The existing one is already close to underside of the bath. I suspect previous installer would have put in right size vent had it been possible. I'll need to have another think about alternate solutions otherwise i'll just go for the aav off the new toilet idea provided thats sufficient.

You're right about no room under the bath The thing is you will end up with 2 aav's which will only let air IN so if you get a drain blockage you will get the toilets filling with water and it won't go away because air needs to get OUT somewhere. I have actually seen this ( in a neighbour's house ) where an aav was fitted instead of a vent. The best way working with what you have is to take the aav off the existing outside pipe and carry it up + over the gutter to open vent. Then go with your new aav inside behind the WC, as you planned.