The Air Admittance Valve

[RVForce2019]

It appears our AAV is in the bathroom cabinet (picture below). However, the tubing is not connected to the drain line, but appears to have direct lines to the tank. Assuming this is the AAV: is this an acceptable design and is there an easy way to convert to a better valve in the future? This one looks difficult to service.


2019 Reflection 290BH
2015 GMS Sierra 3500HD Diesel

[howson]

It appears our AAV is in the bathroom cabinet (picture below). However, the tubing is not connected to the drain line, but appears to have direct lines to the tank. Assuming this is the AAV: is this an acceptable design and is there an easy way to convert to a better valve in the future? This one looks difficult to service.

That's the Atmospheric Vacuum Breaker/Check Valve for the black tank flush.

[RVForce2019]

Thank you Howson: Based on your response, this is not the AAV for the gray tanks. The search continues.

[ThePowells]

Thank you Howson: Based on your response, this is not the AAV for the gray tanks. The search continues.

It will be under the sink off of the drain line. It is up high in the cabinet and usually in a back corner.

[Pete B]

Don’t know if this is still an active thread but thought I’d take a stab. We have an Imagine 2400BH and we have a smell in the bedroom behind the kitchen sink. There is no AAV that I can see unless it is in the wall. I’m assuming it just vents out through the roof but wanted to see if I can get a confirmation on that and any insight into what else could be causing the stink. If it just vents to the roof I’m suspecting a leak somewhere.

[StephenO]

Don’t know if this is still an active thread but thought I’d take a stab. We have an Imagine 2400BH and we have a smell in the bedroom behind the kitchen sink. There is no AAV that I can see unless it is in the wall. I’m assuming it just vents out through the roof but wanted to see if I can get a confirmation on that and any insight into what else could be causing the stink. If it just vents to the roof I’m suspecting a leak somewhere.

Not sure if anything has changed between our 2019 and your 2020 (I highly doubt there are, the 2400 is a fairly popular model, and I believe the only changes are aesthetic), but the only AAV in ours is used on the bathroom drain assembly between the sink and the shower. For the kitchen sink, there is only a wet vent to the roof.

We had a horrific odour once in the front area, but it only occured one time when I was draining the sink after washing the dishes, with a roof vent open and the AC going. For whatever reason, and I still haven't really figured it out, air was pulled back from the roof into the unit through the vent, and goodness it was quite the formidable scent.

[gerri819]

We have a 22 mle. Does the black tank have a aav vent also? Dealing with an odor (presumably sewer gas) that is coming from under the sink where hot water heater is and also behind those drawers.

[howson]

We have a 22 mle. Does the black tank have a aav vent also? Dealing with an odor (presumably sewer gas) that is coming from under the sink where hot water heater is and also behind those drawers.

There are two AAVs in a 22MLE. One is under the kitchen sink and the other is for the bathroom sink. The blank tank is vented straight to the roof. (Not unusual for a gray tank to emit a foul odor.)

Howard

[TucsonJim]

We have a 22 mle. Does the black tank have a aav vent also? Dealing with an odor (presumably sewer gas) that is coming from under the sink where hot water heater is and also behind those drawers.

I checked out the drawing for your 22 MLE. There is no plumbing or vent connection between the black tank and the sink drains. Both of the sinks and shower share a common gray tank. As Howard mentioned, there is an AAV under both sinks. If one of those sticks open, it can smell REALLY bad.

Jim

[Cate&Rob]

Lonestarhowson

Why is an AAV required? . . . When a column of water drops in a vertical pipe it creates a vacuum behind it that can pull the water out of a P trap. This is not a problem if the P trap connects directly to a vertical vent stack (as is usual in a residential situation) since air will be drawn down the vent stack before water is pulled out of the P trap. But, if there is no adjacent vertical vent stack (as is usual in an RV), there needs to be a way to let air in before this vacuum pulls the water out of the P trap. This is what the AAV (Air Admittance Valve) does. Of course, this valve has to be one-way to prevent odours from the drain system from coming back into the RV. Thus, the failure mode of an AAV is when the one-way feature fails and tank odours come back out.

There should be an AAV to go with every P trap drain in an RV unless there is an adjacent roof vent stack (which would be unusual). "Duck bill" drains create a positive seal and do not require an AAV.

Rob

---

Note: Rob's post was copied from https://gdrvowners.com/forum/operati...-rv#post113177 -Howard

[BWSTGDS]

Proactively replaced the stock AAVs in my 377MBS - one in the bathroom and one in the kitchen island.



Thankfully these AAV's unscrewed easily. Mine have a flap that does not always return to the seated position.



Studor 20349