Potter64 Posted March 31, 2019 Report Share Posted March 31, 2019 (edited) Just need a bit of help, daughter has just bought another house needs new bathroom the previous owner had boxed the soil stack 300mm deep 800mm wide enough to sit the toilet against with the sink in a recess back to wall. She wants to fit a vanity unit with matching toilet back to the wall, this is where the problem is the down stairs cloakroom is directly below the bathroom so the soil stack runs the full height of the house into the loft and up to roof ridge what I want to do is cut the stack above the toilet outlet upstairs reduce the pipe diameter to say 50mm until it's in the loft then back to 110, this would mean I could make the boxing in as small as possible allowing a bit more wall to fit units I know I may have to cut the units at floor level so the question is would a 50mm pipe allow enough air into stack to stop it vacuuming Edited March 31, 2019 by Potter64 Quote Link to comment Share on other sites More sharing options...
Ultrastu Posted March 31, 2019 Report Share Posted March 31, 2019 Durgo ? Aka air admittance valve be a solution Quote Link to comment Share on other sites More sharing options...
Potter64 Posted March 31, 2019 Author Report Share Posted March 31, 2019 Its the diameter of the pipe in the bathroom that I want to reduce I just thought as long as it can draw air it woul be ok. Think I need to smash a hole in wall and have a better look Quote Link to comment Share on other sites More sharing options...
Delwint Posted March 31, 2019 Report Share Posted March 31, 2019 As ultrastu said, fit a Durgo valve and then remove the pipe above completely 👍🏼 Quote Link to comment Share on other sites More sharing options...
Jaymo Posted April 1, 2019 Report Share Posted April 1, 2019 https://job-prices.co.uk/durgo-valve/ All simply explained... Quote Link to comment Share on other sites More sharing options...
Old Boggy Posted April 1, 2019 Report Share Posted April 1, 2019 As said above, a Durgo valve is the simple solution. It obviously has to be fitted above the spill level of any basin etc. OB Quote Link to comment Share on other sites More sharing options...
Potter64 Posted April 1, 2019 Author Report Share Posted April 1, 2019 Thanks for the replies will have to see how much room is in the toilet unit Quote Link to comment Share on other sites More sharing options...
figgy Posted April 1, 2019 Report Share Posted April 1, 2019 (edited) Air admittance valve is not always the answer. The stack is not just for drawing g air in but venting too. If possible reroute inside the rear of the vanity to a corner where you can get it into the loft. 2" 50mm pipe should be ok. You can try a durgo and see if it works, I have had the toilet water bounce up and down in the pan as the air in the pipe had no where to vent to basically the durgo created a sealed system with no where to vent the pressure of water wanting to push the air along the pipe. Depends if your underground has a trap in it. Edited April 1, 2019 by figgy Quote Link to comment Share on other sites More sharing options...
Rob525 Posted April 1, 2019 Report Share Posted April 1, 2019 Agree with figgy take a 2 inch up even inch and half if that's all it allowes and maybe stick an anti siphon trap on the basin too 👍🏻 Quote Link to comment Share on other sites More sharing options...
Potter64 Posted April 1, 2019 Author Report Share Posted April 1, 2019 The stack does go up the corner of the bathroom into the loft and to the ridge of roof the diameter of the pipe (4") just makes it a bit tight to get the units in. I just thought if I could half the pipe diameter but still allowing it to draw air and still vent I might get away with it I have found some offset reducers that I could fit leaving what's in the loft 4" and reduce it to 2" in the bathroom itself I can give it a go and see if it's ok I can always reinstate back to original. Good idea the anti Syphon on the sink that will help Quote Link to comment Share on other sites More sharing options...
Old Boggy Posted April 2, 2019 Report Share Posted April 2, 2019 10 hours ago, figgy said: Air admittance valve is not always the answer. The stack is not just for drawing g air in but venting too. If possible reroute inside the rear of the vanity to a corner where you can get it into the loft. 2" 50mm pipe should be ok. You can try a durgo and see if it works, I have had the toilet water bounce up and down in the pan as the air in the pipe had no where to vent to basically the durgo created a sealed system with no where to vent the pressure of water wanting to push the air along the pipe. Depends if your underground has a trap in it. If you do decide on the Durgo, don't forget that it needs to be accessible for maintenance as they can sometimes stick and also need permanent vent to the room in the boxing/vanity unit allowing air to enter. Just a 50mm hole or slot is sufficient. As figgy says, probably best to go the 50mm pipe into the loft, which sounds like what you have already decided upon. OB Quote Link to comment Share on other sites More sharing options...
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