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Old 09-15-2022, 08:57 AM   #1
jsb5717
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40 years of trailering...still learning

I love it when I learn something new. Recently, if we are camping 3 or more days with the storage tanks closed, we started smelling gray water in the rig. Discovered it was coming from under the kitchen sink. This was new, hadn't smelled it the past couple years.

Turns out there's a one-way vent cap in the drain pipe designed to help the system drain faster (at least there is in ours). Also turns out that you can easily replace this vent. Who knew! Well, I didn't. Bought new vent caps on Amazon, unscrewed the old, and screwed on the new...with a little thread tape to seal it.

Anyway, it's that simple. Thought I'd share.
 
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Old 09-15-2022, 09:19 AM   #2
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If you're not learning you're dead. Where is this check valve and what does it look like?
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Old 09-15-2022, 09:29 AM   #3
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Originally Posted by Foldbak View Post
If you're not learning you're dead. Where is this check valve and what does it look like?
I don't have a pic at the moment, but I'll bet your rig has one. Look under your kitchen sink at the black drain pipes. You'll see a vertical leg that goes up to nothing. That's it. I'll get a pic and post it.
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Old 09-15-2022, 09:42 AM   #4
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The original looked a little different, but the function is the same.
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Old 09-15-2022, 09:51 AM   #5
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Thanks Jeff for this info and what to look for.
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Old 09-15-2022, 09:55 AM   #6
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Thanks Jeff I'll take a peek down there!
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Old 09-15-2022, 10:46 AM   #7
Carl n Susan
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That is an Air Admittance Valve that is used in place of a vent stack.

https://www.oatey.com/faqs-blog-vide...ittance-valves
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Old 09-15-2022, 12:52 PM   #8
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I had a deal like that mine was loose, about ready fall out.
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Old 09-15-2022, 12:58 PM   #9
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thanks for the info, good to know
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Old 09-15-2022, 02:29 PM   #10
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Quote:
Originally Posted by Carl n Susan View Post
That is an Air Admittance Valve that is used in place of a vent stack.

https://www.oatey.com/faqs-blog-vide...ittance-valves
I don't suppose their using those on black tanks....
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Old 09-15-2022, 02:33 PM   #11
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My rig is pretty old but my vent valve is in the cabinet/compartment that houses the refrigerator, which sets right next to the sink. Accessible through the exterior vent
panel. The symptoms were exactly as Jeff described.
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Old 09-15-2022, 02:34 PM   #12
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Originally Posted by Foldbak View Post
I don't suppose their using those on black tanks....
A normal vent stack is used for most of the tanks including the black one. The Air Admittance Valve comes into play when there is no place for a vent stack such as in a standalone island.
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Old 09-15-2022, 04:22 PM   #13
Foldbak
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I know but given the problem I'm having I thought humm....that would explain it.
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Old 09-15-2022, 07:23 PM   #14
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Quote:
Originally Posted by jsb5717 View Post
I love it when I learn something new. Recently, if we are camping 3 or more days with the storage tanks closed, we started smelling gray water in the rig. Discovered it was coming from under the kitchen sink. This was new, hadn't smelled it the past couple years.

Turns out there's a one-way vent cap in the drain pipe designed to help the system drain faster (at least there is in ours). Also turns out that you can easily replace this vent. Who knew! Well, I didn't. Bought new vent caps on Amazon, unscrewed the old, and screwed on the new...with a little thread tape to seal it.

Anyway, it's that simple. Thought I'd share.
Jeff ain't that the truth! Sort of sheepish to admit, but I spend a lot of time on the forum just learning from others - just like in this case. Sure has been a great place to land and find new folks to bounce ideas off of too! Glad you nailed down your issue and it was a simple fix.
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Old 09-16-2022, 08:33 AM   #15
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Those vents are only used in locations where venting to the exterior of the coach is not possible. Running a vent stack from the kitchen sink is impossible, but you black tank vents directly to the roof.
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Old 09-22-2022, 08:51 AM   #16
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Coincidently, I had just discovered the air admittance valve as the source of our under-sink stink.

BTW, the air admittance valve is a one-way valve, the purpose of which is to prevent losing the water seal in the P-trap.
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Old 09-22-2022, 07:41 PM   #17
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I put black tank treatment in the gray tanks
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Old 09-25-2022, 06:37 PM   #18
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Quote:
Originally Posted by bad moon View Post
coincidently, i had just discovered the air admittance valve as the source of our under-sink stink.

Btw, the air admittance valve is a one-way valve, the purpose of which is to prevent losing the water seal in the p-trap.
me too!!!!!!!!!
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Old 09-25-2022, 08:28 PM   #19
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Check the vent pipe
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Old 10-04-2022, 05:38 PM   #20
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I had also heard you could put a plastic bag very loose over the vent and use a rubber band to seal it to the pipe. Made some sense. Loose would allow it to draw aire down fr quick flush ... food for thought
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