AAV installation

Let me start by stating that I'm a DIY'er . . .

I'm completely re-doing my master bath from the ground up. Got all the plumbing done and ready to finish all the drains. Although all of the fixtures have been relocated, there is a main vent stack in the corner of the bathroom dedicated to this bath, which also has a separate septic discharge and tank. (Yes, I have 2 septic tanks, each with its own field.)

I only moved the toilet 7 feet across to the other side of the room and the drain was easy enough to re-route. The sink is only moved about 6 feet from its original location also. The tub/shower is the farthest away at the opposite end of the room and is now about 11 feet from the vent stack.

My original intention was to install an AAV on a wye just downstream of the tub trap. The valve would then be installed inside a wall cavity above the tub and sink height. I wasn't positive I really needed it, but thought it would do no harm. After reading some old posts, I'm not so sure now. I don't want it to malfunction and have problems.

Should I just forget about installing an AAV and everything should work OK?

Thanks

If you have the walls open, why not run proper vents to the existing vent stack? FOrget the AAV unless that won't work. You need access to an AAV for replacement when its time comes...it must remain accessable. If you could sketch things up, it would make things easier to understand what you have and where things are.

An AAV is a mechanical device and has to be where you can change it. If you need a vent, you need a vent. Be sure it is at least 6" above the flood plane of the fixture it serves. Be sure it is OK to use with your local code.

Why not just run a real through the roof vent?

AAV's are just a poor substitute used by lazy people that are too lazy to put in a few extrat feet of pipe.

I'm not trying to be lazy about doing it right, but with a fresh foot of snow on the roof, I don't want to be up there poking holes. As I originally stated, I'm not sure if I even need to add the extra vent. The existing 3 or 4" vent stack that serves the whole bathroom is still there and inline. The only reason I question the need for an additional vent is because I have moved the tub drain 3 extra feet away (10-11 feet total). My new thought after all of your replies is to run the new vent through the wall and up into the attic. This way the AAV is accessible with only the 1-1/2" vent pipe in the wall. I can then always extend it through the roof in the future if necessary.

Or maybe you guys may tell me I don't need to even bother with it . . .

I guess it can't hurt to put the pipe in the wall anyway. It will be accessible in the basement and the attic.

Thanks for all the help!

It is as simple as tying into that existing vent before it goes out the roof.

Do any of your fixtures have vents now or do they just run into a 4" stack which is vented? I would make sure everything is individually vented and tie everything into that 4" stack. No new roof penetrations necessary.

Redwood said:

It is as simple as tying into that existing vent before it goes out the roof.

Click to expand...

A lot more of a PITA if it's cast iron, no?

A lot more of a PITA if it's cast iron, no?

Click to expand...

Thats what snap cutters are for.
It takes maby five minutes to set up and snap a section out.

The stack is copper. But the problem is that there is no access in the walls, only in the attic . . . and the tricky part is that I have a 4/12 pitch roof with the stack close to the eave. Leaves me about a foot to crawl in and try to tie into. This is why I though about "temporarily" installing an AAV in the attic. When the weather's nice I can then extend the 1-1/2" PVC vent through the roof.

To work properly, each trap should have its own vent. How far away that vent is is determined by how big the pipe is. I think on a 2" line, it is 5' max (don't quote me!). It gets shorter for smaller and longer for bigger. If it is big enough, it probably doesn't need its own vent, as you could never fill the pipe so there's room for air to move either way. So, yes, you could run the individual vents up into the attic after attaching them close enough to the fixtures they are serving, tie them together and vent through the roof, put it on an AAV, or tie into the existing vent. Having the vents too far away, risks poor performance and siphoning them dry when something else drains, leaving the drain open to the sewer, which may not be very pleasant or healthy.

aav

It makes not difference where the old fixtures were relative to the new ones, in most cases. How they have to be vented depends ENTIRELY on how the new fixtures are piped, just as it would if they were a completely new installation without any previous connections.