Trap/venting question

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Mckeand13

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Hi everyone,

Looking for some advice on how to correctly fix this situation. I just moved into this house and have had a couple instances of the washtub trap going dry (evaporate or siphon, not sure) resulting in sewer gas coming back into the room.

The washtub is rarely used, but I definitely want to keep it. The iron filter backwashes a good amount of water into its own standpipe but that appears to be plumbed as an “S” trap. The sewage basin the drain line runs into has a large pump in it that moves a lot of water quickly.

From my unprofessional understanding, it seems that the washtub is lacking a vent. Being in the basement with no other plumbing around, There’s really not a good way to tie into a vent either. Would it be acceptable/advisable to put an AAV just after the washtub trap?

Is the standpipe for the iron filter ok as is relative to venting? Does the vent in the sewage basin (which is tied into the homes vent stack) serve as an acceptable vent for the standpipe? I believe it would be recommend/ideal to turn the long turn wye on its side so it can be changed to a “P” trap?

I would add pictures but it’s hard to capture the details. Most of it is hidden behind iron filter, water softener, and water heater.

Thanks for your help!
 

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wwhitney

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AAVs are apparently not allowed by the MN plumbing code, the UPC. So the proper way to address this is to provide a dry vent takeoff that connects to a vent through the roof. Your new vent can tie into an existing vent at an elevation that is 6" above the flood rim of all the fixtures served by either vent. Since this is a basement, you'd need to open up a wall on the floor above to make that tie in.

Having said that, an AAV would be a less bad solution than what you have now.

Each of the washtub trap and the standpipe trap needs a vent connection, either a dry vent or, in states that allow them, an AAV. That needs to come off the horizontal trap arm before that trap arm falls more than one trap diameter. For the UPC, the vent connection also has to be within 42" of run from a 1-1/2" trap and within 60" of run from a 2" trap.

Cheers, Wayne
 
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