Best of a Bad S-Trap Situation?
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This is an individual branch AAV, therefore it is not required to be above the flood rim of the fixture.
IPC 918.4 Location.
Individual and branch-type air admittance valves shall be located a minimum of 4 inches (102 mm) above the horizontal branch drain or fixture drain being vented. Stack-type air admittance valves shall be located not less than 6 inches (152 mm) above the flood level rim of the highest fixture being vented. The air admittance valve shall be located within the maximum developed length permitted for the vent. The air admittance valve shall be installed not less than 6 inches (152 mm) above insulation materials.
Individual and branch-type air admittance valves shall be located a minimum of 4 inches (102 mm) above the horizontal branch drain or fixture drain being vented. Stack-type air admittance valves shall be located not less than 6 inches (152 mm) above the flood level rim of the highest fixture being vented. The air admittance valve shall be located within the maximum developed length permitted for the vent. The air admittance valve shall be installed not less than 6 inches (152 mm) above insulation materials.
Wouldn't the vent pipe still need to stay "vertical" until the AAV or flood rim, whichever came first?
I'm not sure what you're asking. Look at the picture in my post. The AAV can be located under the sink. The flood rim is irrelevant for AAV venting of individual fixtures.
Oh, I just realized what you're asking about: the lateral offset in the OP's diagram. Yes, the vent needs to be vertical. But the point is that there's no reason to have a lateral offset. Just install the AAV under the sink and be done with it.
In the picture in #1, there doesn't look to be clearance under the sink for the AAV. But if there is, then that would be good.
There should be plenty of clearance if he lowers the P-trap.
Also, the AAV can often be tucked up higher between the sink bowl and the back wall to gain additional vertical clearance.
javelindesign
New Member
Thank you both! So, glad to hear about the AAV - since the drain in the floor is UNDER the sink.. I'll play with it to put the AAV under the sink if possible. Sounds to me like I'll have to do a vertical extension from the sink drain though to bring the P trap low enough to get the AAV in right? The actual trap will be pretty close to the floor? Thanks in advance!
Jadnashua
Retired Defense Industry Engineer xxx
An AAV can be contaminated if waste gets pushed into it, so it's advantageous to get it as high as possible after the p-trap so a backup is less likely to damage it. FWIW, they also do eventually wear out, so you need to put it in a location that can be accessed. In say a kitchen or vanity situation with the waste going into the wall, you'd get the vertical arm high enough to be close to the bottom of the adjacent counter, while still being able to unscrew it during installation, or when it fails.
FWIW, a 45 or greater angle is considered 'vertical' for vents, if you can work that in to get it higher for more reliability. If it never backs up, it wouldn't be an issue.
FWIW, a 45 or greater angle is considered 'vertical' for vents, if you can work that in to get it higher for more reliability. If it never backs up, it wouldn't be an issue.
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Don't try to extend the existing drain's tailpiece (the part that drops from the sink to the P-trap); buy a new one that's longer and cut it to the length you need.
As I stated earlier, there is often room behind the sink bowls to fit an AAV so it's above than the bottom of the sink. It doesn't have to be higher than the bottom of the sink, but it does need to be a minimum of 4" above the top of the trap, and higher is better.
Instead of making your drain drop vertically from the sanitee to the drain in the floor, you can position the sanitee near the wall at the back of the sink, put the AAV on a vertical extention out the top of the sanitee, and then put your offset in the drain below the sanitee to get back to where it enters the floor. This way, you don't have to deal with any offsets in your vent line (which is usually impossible to do in the vertical confines under a sink since your vent line cannot go horizontal).
If you need to or want to install the AAV up behind the sink and access is limited, you can make it easier to service the AAV by putting a threaded coupling at the top of the sanitee, then add your vent riser and AAV. That way, you can remove the vent riser and AAV together from the sanitee. Easier than trying to reach up behind the sink to unscrew the AAV from the top of the vent riser. Make sure all threads are properly sealed.
javelindesign
New Member
Hey all, just thought I'd post a couple of pics to final outcome. The AAV is against the wall RIGHT below the top edge of the sink below where the faucet is. I filled the tub with water a few times and pulled the stopper... all the water rushed out, engaged the AAV and left water in the trap as hoped, so I think it's good to GO!
Thank you all for your advice.
Jay
Thank you all for your advice.
Jay
javelindesign
New Member
Yep! As Mliu suggested, there is enough room between the tub and the wall to access the AAV if needed in the future. Probably not perfect all around, but short of digging up the concrete and wall, a pretty good solution.. At least good enough for me! Thanks again to all!
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