Hi, I'm trying to configure a basement bathroom rough in using AAV's with a vanity, shower and toilet combination. Also, we have a back water valve that is being relocated in the mechanical room for access and with everything tied in behind the valve. This seemed to be the best system we could come up with. We have a 1.5 inch aav for under the vanity and a 2 inch aav in the wall between shower and toilet. Not sure if this will pass inspection. I pulled permits so this needs to pass code. Any advice is appreciated.
Basement bathroom plumbing no roof vent
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wwhitney
In the Trades
Since you mention AAVs, I take it you are under the IPC? You don't need the AAV in the wall between the shower and WC. The single AAV at the lav is sufficient for the lav to wet vent the shower and WC.
If you do add a dry vent/AAV in between the shower and WC, the dry vent takeoff has to be vertical, and stay vertical until 6" above the associated fixtures, which I guess would be the lav and shower. So you'd have to reroute your drain line closer to the wall, you can't have the dry vent go horizontal under the slab.
Cheers, Wayne
If you do add a dry vent/AAV in between the shower and WC, the dry vent takeoff has to be vertical, and stay vertical until 6" above the associated fixtures, which I guess would be the lav and shower. So you'd have to reroute your drain line closer to the wall, you can't have the dry vent go horizontal under the slab.
Cheers, Wayne
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AAVs only protect against negative pressure, not positive. Water falling down the stack from above can cause positive pressure. Whether it passes inspection or not a basement bathroom only using AAVs is subject to having trap seals broken by that positive pressure.
Thank you, good to know. Much appreciated.
Okay, thanks what would you suggest since we have no access to a vent pipe to the roof?
James Henry
In the Trades
https://ipscorp.com/plumbing/wp-content/uploads/2021/02/Studor_Technical_Manual.10th-Ed.2018-1.pdf
For your reading pleasure.
For your reading pleasure.
As long as your lines are not clogged downstream, the positive pressure should be able to be relieved by the other things joining that flow are vented through the roof. If you have septic, and your toilet starts flushing slower, get the septic tank pumped. You are probably proactive on that anyway, because you never want the septic tank to get anywhere near full. I am not a plumber.
If you are on sewer, consider adding something to prevent backups. Do sewers ever back up in your area due to big rainstorms? If so, consider re-designing to use overhead sewers. That term may not mean what you first suspect it means.
What is the big circle with an L in it, and a BW next to it? I think you may want to run the output of the L-BW via a wye to join the other drain.
If you are on sewer, consider adding something to prevent backups. Do sewers ever back up in your area due to big rainstorms? If so, consider re-designing to use overhead sewers. That term may not mean what you first suspect it means.
What is the big circle with an L in it, and a BW next to it? I think you may want to run the output of the L-BW via a wye to join the other drain.
Good move. The ones that are normally open are better than normally closed. The ones with a flapper will pretty much always be held open after a time with debris.
Just something to look up if you like. I don't have experience with the normally open myself.
DIYorBust
Active Member
You can wet vent a toilet to a lav AAV under IPC?
Jeff H Young
In the Trades
the back water valve should take care of positive pressure from floor above waste. not a big fan of the aav but should work
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