Where is my Air Admittance Valve

[Lhinkle114]

Can someone help me, we have a 2019 3791RD and I am trying to find out if I have an air admittance valve in under my bathroom sink. We have been getting a sewer smell lately when we run the sink water and I can’t find out why. Someone suggested stale washer and dryer water hoses, but we use those appliances on a regular basis. So I did some digging and thought the air admittance valve might need replaced. I found one in the kitchen but not in the bathroom unless it is hidden in the wall. If you look at my pictures there is a black pipe going up in the wall behind the sink. I also hear a Radom clicking sound coming from inside the wall when I run the faucet which might be the air admittance valve. But if this is it how do I replace it without tearing out the wall? I circled the point when I think it is

Thank you in advance
Larry

 

[Mikendebbie]

Here is my wild as sed guess…
A - washer vents thru roof
B - bath room sink has air valve
C - toilet vents thru roof
D - kitchen sink has an air valve

Get up on the roof and count the vents.

 

[Carl n Susan]

Since stale washer lines have been eliminated, here are my guesses on your configuration.

• The washer drain runs down to the outside wall and then along the wall (in the raised portion) to the pass-thru compartment where it goes down to the sink/shower drain line.
• The sink drain line, in the picture, is also the vent. There is no air admittance valve. The sink drain connects to the shower drain in the pass through area.

How they actually vent while draining it what I don't understand. Perhaps the Hepvo valve in the shower drain serves a dual purpose. I do know my sink/shower and, subsequently, washer drains are plumbed in this manner.

I dislike the 90 degree and 45 degree fittings in the vent line. I have a similar setup in the kitchen which broke at the upper 45 degree connection (likely frame flex symptom). I would double check that the under sink drain line to ensure there is no breakage/leak.

 

[RMcNeal]

Just to answer your original question, the "air admittance valve" is on the top of the two white pex lines in your picture. They are next to the red pex (hot water) and blue pex (cold water) lines that feed the sink.
It starts from the black tank flush connection in your convenience center up to the valve, then back down to the black tank flush sprayer.
It serves as a vacuum breaker and backflow preventer for the black tank flush line.

 

[Lhinkle114]

Thank you for all your help, I looked on the roof and there is a vent directly above the pipe, that being said where is the filter to prevent and gases from releasing through the roof or maybe the pipes below are connected to a hepflow off the shower. Next step follow the pipes underneath, but that won’t explain the clicking sound behind the mirror when I run the water

 

[RMcNeal]

AFAIK, there is no filter on the drain vent pipe. The shower does have a HepVo valve under the shower.
If your smells are only coming from the water in the sink when running water, then you likely have stale water in the water lines. As stated above, that is also likely coming from the water lines that feed the washer. If you do not have a washer, then the water in those lines just sit and stagnate since no water runs through them, ever.
I added shut off valves to those lines under the bathroom since I too do not have a washer at this time. You might try hooking up a hose to the washer lines and flushing some water through them. You can either run it into a bucket, the drain line for the washer, or if your hose is long enough, run it outside.
I put in shut off valves in the lines with a drain on them so I could drain the water from the line past the valve and prevent it from sitting and going stale.

 

[RMcNeal]

The shutoff valves also mean there's less water line to winterize, if you ever do that.

 

[jcurtis934]

All above are good inputs. My guess is that the hepro for the shower drain is not fully closing and you get the grey tank odor that way when using the sink. Those valves are just a rubber tube the is deformed in a closed position and shower drain water forces the tube open to drain that water. MINE never did fully close even after taking it apart and cleaning it. I replaced it with a heavy duty p trap and used no hub rubber coupling to put in the p trap. Clicking in the wall...could be the vent pipe moving slightly??? Who knows what that is. John

 

[Lhinkle114]

Wow, all great advice. I want to thank everyone for their input sometime this week I’ll be crawling in and removing the walls and trying to follow the line. See if I can get any further knowledge on what the problem is. But I know it’s not the washer and dryer waterlines do the fact that we use the washer and dryer once or twice a week. Otherwise, everything else great suggestions I will keep looking and keep everyone informed

 

[Carl n Susan]

I looked at Bob Rohrman's water system diagram and it sure looks like the Water Heater Bypass valve does shut off the cold water to the water heater.

https://www.montanaowners.com/forums/attachment.php?attachmentid=10473&d=1635646602

 

[Lhinkle114]

Great diagram that’s another thing to look into

 

[Frank64-MOC]

Air Admittance Valve

I too had the same smell situation going on with my 3791rd. I started out flushing the washer machine line and this eliminated the smell. Eventually I installed cutoff valves as McNeal suggested. See his post.
I thought originally when I I de winterize the system I was good to go. However a few months later the smell became stronger. When draining this washer machine hook up i saw the “ pink” anti- freeze liquid coming out.. The water is stagnant. Need to eliminate or remove