Toilet back flush problem

[Expertboy]

Hi,

I have 3 bathrooms on 2 floors, and 2 of the toilets on the ground floor are back to back of each other and sweep into the same soil pipe.

The problem i'm getting is that when i flush one of the toilets that are back to back on the ground floor, the flushed contents of either one backs up into the other toilet? no matter which one is flushed!

There is only 1 sub stack on the ground floor and obviously the upstairs is vented up to the eaves.

Anyone got an idea on how to cure this?

 

[Nige F]

You can get a 1 way valve - mac alpine I think also stops rats

 

[HERTS P&D]

Is this a new problem? if so you may have a blockage.
If not then the pipework will need to be altered.

Andy