2 toilets from 1 horizontal pipe

[chan007]

We are renovating the family bathroom and have changed the layout. In the new design, the toilet position has been relocated, and we connected it to the existing soil pipe using a Tee fitting in the elbow to extend the pipe. T position is sideways as it is directly connected to the elbow and existing toilet. Although we haven't installed the new toilet yet, we tested the setup by flushing coloured water through the new toilet pipe. I discovered that this water flows back into the existing toilet through its built-in S trap. Can someone suggest how we can resolve this issue?

 

[CountryFan]

Are you sure it's an S-trap? Seems quite close imo. Is there a blockage anywhere? Could be cross-flow

 

[chan007]

Are you sure it's an S-trap? It seems quite close, IMO. Is there a blockage anywhere? Could be cross-flow

I am not 100 % about type of trap we have inbuilt in toliet. There is no blockage as we have replaced the pipes. It is cross flow to the existing toilet from new toilet. How can we resolve this

 

[CountryFan]

You've replaced the existing soil pipe??? It's been a while since I've done one, but you may be able to change the elbow that goes to existing toilet and change for a branch and connect off that.

 

[Madrab]

Erm, not the way a double branch is supposed to be used, it's a branch, not a Tee. A double branch is designed to transition 2 horizontal soil pipes into a vertical soil pipe, as in pic one > grey branch middle right, it's not meant to be flat on it's side and used as a Tee. Each toilet should have it's own down angled single branch connected into the horizontal soil pipe. The volume of water from a toilet down one leg will always crossflow into the other leg like that.

 

[chan007]

Erm, not the way a double branch is supposed to be used, it's a branch, not a Tee. A double branch is designed to transition 2 horizontal soil pipes into a vertical soil pipe, as in pic one > grey branch middle right, it's not meant to be flat on it's side and used as a Tee. Each toilet should have it's own down angled single branch connected into the horizontal soil pipe. The volume of water from a toilet down one leg will always crossflow into the other leg like that.

Unfortunately, don't have enough space to run 2 seperate pipes

 

[Madrab]

Unfortunately, don't have enough space to run 2 separate pipes

Unfortunately it's not going to work properly the way it is. The design of the space should have been created with that in mind.

There's a reason they don't have 110mm Tee's, there's too large a volume of water from a toilet to allow it and for it not to suffer from crossflow/syphoning.

 

[chan007]

Unfortunately it's not going to work properly the way it is. The design of the space should have been created with that in mind.

There's a reason they don't have 110mm Tee's, there's too large a volume of water from a toilet to allow it and for it not to suffer from crossflow/syphoning.

Can we solve the problem if I change the elbow position. Current set up is number 2 . What if we change to set up 3? Obviously, it will add another 90 degree bend in pipe.

 

[Madrab]

As long as setup 3 - T1 uses a single swept branch then yes. That T1 branch should also be angled upwards or vertical. Of course adding more bends certainly isn't ideal but if there's no other way around it. The other concern would be fall, have you got the min fall on that run, the more the better.