Adding toilet to soil stack

[Steve2178]

Hi,

I have an old cast iron pipe that needs replacing and I want to remove it completely and divert an upstairs toilet to the second soil stack I already have a few meters across the wall.

the second soil stack already has a downstairs toilet on it.

I would like to know more as I’ve been informed by a plumber that if I add a second toilet to the top of my other soil stack I could force the water into my downstairs bathroom out of the toilet bowl due to the pressure?
im sure I’ve seen many houses with more than one toilet on a soil stack so can anyone confirm if this is correct or what precautions need to be done to ensure this setup is ok?

here’s a photo so basically I want to put a pvc elbow where the cast iron branch is coming out of my wall and run a horizontal pipe with a slight drop around 3m across to the other soil stack.

I want this pipe completely removing and I plan to remove the hopper and downspout too as I’m extending my conservatory and this wall is going to be an interior tiled wall. I don’t want to have a pipe on my inside wall and or box or in as to waste space.

 

[Aquarius]

I don’t personally see the issue with your proposal. Old Blocks of flats have toilets on each floor sharing a stack, and they don’t have issues.

 

[Steve2178]

I don’t personally see the issue with your proposal. Old Blocks of flats have toilets on each floor sharing a stack, and they don’t have issues.

That was my thought. He mentioned something about pressure building up in pipe and causing downstairs toilet to be effected somehow by it?

 

[Pickwickpick]

That was my thought. He mentioned something about pressure building up in pipe and causing downstairs toilet to be effected somehow by it?

What was he proposing? Or was he claiming it just wasn't possible?

 

[Steve2178]

What was he proposing? Or was he claiming it just wasn't possible?

He said highly recommends I don’t do what I propose and instead just replace the entire cast iron with pvc but that defeats the purpose of me wanting a clear wall to tile

 

[Pickwickpick]

He said highly recommends I don’t do what I propose and instead just replace the entire cast iron with pvc but that defeats the purpose of me wanting a clear wall to tile

Weird, it is really common to have multiple toilets on the same soil stack.

 

[Steve2178]

Weird, it is really common to have multiple toilets on the same soil stack.

so if I go ahead and use a different plumber who said he’d do it no problem he ain’t a cowboy? I won’t have issues with downstairs toilet?

 

[king of pipes]

Can you add some more pictures please ?? of what is connected and internally. Kop

 

[Steve2178]

Can you add some more pictures please ?? of what is connected and internally. Kop

Can’t see the pipe internally as it’s behind a fitted toilet with the cabinet thing at the back. But that’s all it is. Two toilets. One upstairs one downstairs.
Both plumbers I’ve seen havnt even bothered looking inside

 

[Aquarius]

That was my thought. He mentioned something about pressure building up in pipe and causing downstairs toilet to be effected somehow by it?

He might have been trying to say it could pull the trap, but usually happens when there’s a blockage, or if they’re installed in a way against building regulations document H, one example being crossflow connections. I live in a newly built property (2010) and I have 2 toilets connected, albeit on the same level. Just reviewed the photo, does the new stack discharge into a gulley? - this might be the problem.

 

[Pickwickpick]

Sounds like the plumber is concerned about pulling the trap, but even if the new branch is going to be over 6m it can be dealt with by using an internal aav or venting to air so shouldn't be an issue.

@Steve2178 you mention a second plumber, did he also think it was not feasible?
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so if I go ahead and use a different plumber who said he’d do it no problem he ain’t a cowboy? I won’t have issues with downstairs toilet?

WHat length is the branch going to be from the toilet to the pvc soil stack? Also just to confirm, that black pvc soil stack it connected directly to the underground drain and doesn't discharge into a gully?