Air Admittance Valve Question

R.Oak · Jun 5, 2014

Hi guys, first of all please excuse my crude attempt at a drawing. The camera on my phone has broken so I have had to draw a picture to show what I am talking about.

I have a question regarding Air Admittance Valves. Currently the soil stack from the first floor WC drops to ground floor, enters the conservatory and goes to drain with a sub stack about 900mm about the swept T piece.

My customer would like the sub stack above the swept T taken out, with the AAV dropped down the the T so that he can box the the whole lot in and build a little bench over it all.

Im wondering if this will any impact on the running of the soil stack. The ideal situation would be to extend the primary stack up to roof height and have it vent to atmosphere. There is a slight access issue with doing this and the customer would rather reduce the unsightly sub stack in his conservatory.

I am not the most up to date person on soil stack regs, and im not too sure about this if im honest. Im wondering if anyone offer some advice on the issue please? Thanks guys.

Ermintrude · Jun 5, 2014

Don't put in AAV out in an access plug. Access plug for ridding out blockages. U can reduce primary stack to 75mm to get through roof.

R.Oak · Jun 5, 2014

Ermintrude said:
Don't put in AAV out in an access plug. Access plug for ridding out blockages. U can reduce primary stack to 75mm to get through roof.

Thanks for the comment. The access issue for extending the primary stack is down to not physically being able to get up there. The only route would be between the two windows but the conservatory blocks the ladder.

This may be a silly question. But would I be able to change the high level elbow for a T and put the AAV there? So it is just underneath the window, with just a low level access cap where the sub stack used to go?