Minimum size of an aav off a stub stack

[Dannypipe]

Anyone know the regs with this.

Got two commercial toilets to refurb. The client wants to box (with access panels) the stub stacks. Currently they have an AAV on each.

I seem to remember you can buy a type which can be beneath the overflow height of the lowest sanitary item, but the idea that has been floated is to stick a smaller AAV on the top and vent it up through the suspended ceiling.

Any ideas on minimum size? I would have thought 2" would be OK but will have to dig out my WRAS book if no one on here knows! Ta.

 

[AWheating]

needs to be 3" on the end of a stack run.

did a job a few months back where there was 50mm vents and aav's fitted and building control made us increase to 3". the aav was more or less the same size as a 4" one.

 

[plumber0808]

Yes as above,3inch. I had to find this out not to long ago.
It should be able to provide similar ventilation as a vented stack which is 3inch minimum.

 

[chris watkins]

How did you get on with this one Danny ? Was there no way you could get a 50mm say, to the out side to vent both (as commercial Part H should not apply).
Were they suggesting the AAV should go in the ceiling void ?

 

[Dannypipe]

Hi Chris, I haven't started it yet! I've won the work and plan to run 3" pipe up to the ceiling void and fit the AAV's in there.

Can't get the stacks outside to vent, it would be much more work. I'll prob be doing the work in around a weeks time.

 

[JCplumb]

I've been out to look at a stinky AAV in a commercial building today. They had a 2" one on an adaptor on top of an internal stub stack. Going back tomorrow to swap it out for a 4" one and cut/cap a dead leg that runs downhill away from the stack. It services urinals so I'm hoping to catch a cold before I get there...

 

[Dannypipe]

Nice. So a 2" is def' out of the question!

Why I wonder did someone leave a dead leg running down hill away from the stack? Fools.

 

[JCplumb]

No idea, possibly a rodding point at one time, but never clipped and it's about 5' long so it now runs downhill. Will just cut it back and stick a double socket coupler on there with an end cap to allow for access if needed in the future.
What really struck me as odd about the job was the fact that it's a meter installation company with a fleet of gas engineers and they call me out to a plumbing problem...

 

[Dannypipe]

Meter installers don't do plumbing generally!