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Old 01-24-2021, 10:19 AM   #1
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Air Admittance Valve vs Automatic Vents

I'll admit to being a novice in plumbing system design, but in the process of tracking down the source of recurrent sewer fly infestations, I've learned a bit about the small, under-counter devices called "air admittance valves" or "automatic air vents". They are used to provide air into a sewer system in locations where a roof vent would be difficult to install.

Normally, these devices are the sorts of things you never need to replace but they can go bad with age which can result in sewer gases and, sometimes, sewer flies, getting into your RV. Furthermore, it appears that the RV industry is still permitted to use spring-loaded automatic air vents which are no longer allowed in fixed structures, having been replaced by air admittance valves which don't have springs and, therefore, are supposed to last longer. In typical RV industry style, rather than use a ~$15 air admittance valve, they use an "outlawed" device to save a buck or two!

Most of the YouTube videos I watched on this topic don't distinguish between air admittance valves and automatic vents, but the devices they show being removed from their RVs are the same black, spring-loaded automatic vents I found in mine. Some of the videos even mention replacing the spring-loaded ones with a high quality AAV but don't mention that the device being removed is not an AAV, but, rather, an automatic air vent.

The good news is that these valves are usually screwed into the sewer pipe and are fairly easy to remove, assuming you are limber enough to reach them under the sink. I've read about some being glued in place, but that's not in accordance with normal practice.

You probably will find them under your kitchen and bathroom sinks and also, possibly, associated with your shower and washer.
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Old 01-24-2021, 10:47 AM   #2
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Quote:
Originally Posted by docj View Post
I'll admit to being a novice in plumbing system design, but in the process of tracking down the source of recurrent sewer fly infestations, I've learned a bit about the small, under-counter devices called "air admittance valves" or "automatic air vents". They are used to provide air into a sewer system in locations where a roof vent would be difficult to install.

Normally, these devices are the sorts of things you never need to replace but they can go bad with age which can result in sewer gases and, sometimes, sewer flies, getting into your RV. Furthermore, it appears that the RV industry is still permitted to use spring-loaded automatic air vents which are no longer allowed in fixed structures, having been replaced by air admittance valves which don't have springs and, therefore, are supposed to last longer. In typical RV industry style, rather than use a ~$15 air admittance valve, they use an "outlawed" device to save a buck or two!

Most of the YouTube videos I watched on this topic don't distinguish between air admittance valves and automatic vents, but the devices they show being removed from their RVs are the same black, spring-loaded automatic vents I found in mine. Some of the videos even mention replacing the spring-loaded ones with a high quality AAV but don't mention that the device being removed is not an AAV, but, rather, an automatic air vent.

The good news is that these valves are usually screwed into the sewer pipe and are fairly easy to remove, assuming you are limber enough to reach them under the sink. I've read about some being glued in place, but that's not in accordance with normal practice.

You probably will find them under your kitchen and bathroom sinks and also, possibly, associated with your shower and washer.
You make a very good point with this post, that the use of the term AAV is most often incorrect when applied to RV discussions because most RVs use the black Automatic Air Vents.

However, I would not condemn the RV industry for use of the cheaper devices. They were "outlawed" in permanent structures due to their possibility of failure, whereas the true AAV has a usable life of approximately 30 years. Automatic vents are not illegal, and I know you did not imply that, so using them in a RV is perfectly appropriate. Both devices perform the same function, when they function. Not too many RV manufacturers expect their product to last for 30 years or more so they don't include components to outlast their product. Adding a plumbing device that costs 3x more than another that works just as well is a business decision that may not make good sense, especially in an industry where keeping the price point low is a top priority.

When the Automatic vents fail, your post is critical in making the decision on how a replacement will be decided. Knowing there is a difference between an Automatic Air Vent and an AAV is valuable for the owner as it accounts for the wide variation in price between the two devices.
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Old 01-24-2021, 10:55 AM   #3
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I'm thinking failure of these devices is less important in an RV as they are only single level.
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Old 01-24-2021, 12:22 PM   #4
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I'm thinking failure of these devices is less important in an RV as they are only single level.
In my case the 20-year-old automatic air vents weren't sealing well enough to prevent drain flies from getting in. Single level vs multi-level wasn't an issue.
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Old 01-24-2021, 11:10 PM   #5
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AAVs/Auto Vents

They FAIL and the cheap ones used in RVs fail routinely
https://www.irv2.com/forums/f258/air...ve-502398.html

https://www.irv2.com/forums/f115/air...ue-470019.html

https://www.irv2.com/forums/f59/air-...ve-458154.html

https://www.irv2.com/forums/f278/air...ve-385227.html

https://www.irv2.com/forums/f50/air-...nk-319001.html

And On and On and On ---------
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Old 01-26-2021, 06:47 PM   #6
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I replaced all of mine with Oatley valves. I was chasing smells and that was part of what seemed to be a 10 prong approach, lol. After I went through all of the changes we also then started, and religiously use, Happy Campers. We never get smells while parked and rarely get a smell going down the road.

Those smells can be nasty and glad they are gone. For now.
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