Roof pincushion

[santhony7]

I am currently renovating a 1940s home 100% solo. I am adding two bathrooms back to back and was wondering how to avoid turning my roof into a pincushion of vent stacks. All and all I want to do things the right way but what is the best way to reduce the amount of vents through the roof? Can I just put a single 3" stack through the roof that all fixtures connect to in the attic? I would use AAVs but they say you have to provide access to them and I won’t be having any vanities to tuck them into (all pedestal sinks). Can you put AAVs in the attic? Thanks for any advise!

[jimbo]

Assuming you already have at least one vent penetration through the roof, depending on how large it is you could tie all the new vents to it in the attic. It might be easier to make one more penetration to handle the 2 new baths.

Not every code allows AAV at all, and many will only allow it in unusual circumstances where a proper vent would be difficult or impossible. Your case would not qualify.

[santhony7]

Yea, I already have on cast-iron main stack at 3" but I was just going to go ahead and put another 3" that all of the new fixures tie into since that main 3" stack is about 30' from the new fixtures. Studor make an AAV that can have up to 500 DFUs but you are saying that most codes don't allow it?

http://www.studor.net/products/maxi-vent_UK.asp