Air admittance valve acceptable??

[Fireboy24]

Hi there, I have a 50's ex council maisonette with cast iron stack. Customer wants toilet moved from ground floor to first floor. It's not possible to cut and tee into the stack and replace everything above the toilet in plastic as there is no access to the roof etc. I was thinking instead I'd cut the stack on 1st floor, put the tee in and then leave an air admittance valve there meaning I no longer need to connect into the open vent at roof level. That bit above the new loo could just be left redundant/sealed off. Anyone see any probs with this??

thanks in advance

 

[Ch4 plumbing]

Well the first issue would be that without the bottom of the stack for support the top bit could come away over time and harm someone, might be a small risk but a length of 4" cast soil on the head would ruin anyone's day!

 

[Fireboy24]

Well the first issue would be that without the bottom of the stack for support the top bit could come away over time and harm someone, might be a small risk but a length of 4" cast soil on the head would ruin anyone's day!

Hi there. Thanks for the response. Sorry should have mentioned originally that I was gonna build supports for the redundant upper part! I'm more wondering wether there has to be something venting to open air or wether ou can have a main stack with an AAV as the only means of venting?

 

[Ch4 plumbing]

Their has to be at least one SVP on each branch back to the main drain, if you've got that then you should be ok, I'm not 100% sure wether AAV's are okay for outside use? I've never done it that way before tbh.

 

[Simon F]

as above, I see loads near me on aav outside.
it should have the BBA approval for outside use

 

[josh]

Unless in certain circumstances every property as a rule should have a vent to atmosphere. Building control wouldn't pass it otherwise, the head of the drain should have the vent to outside (the furthest soil stack from the man hole).
Just for those who don't know, you can't put AAV's on drainage systems that are on septic tanks, as the pressures are different in a septic tank system.