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Old 05-04-2019, 02:11 PM   #1
RitchieD
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Question Plumbing Cap under sink?

Newbie. What's the purpose of the capped up-pipe under the sink? Should the cap be on and tight?
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Old 05-04-2019, 02:26 PM   #2
66joej
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Looks like a vent to allow water to drain to the grey tank.
No it should not be on tight.
And welcome to the forum from Radium Hot Springs BC.
If you are from Greely CO had friends there.
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Old 05-04-2019, 02:31 PM   #3
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Quote:
Originally Posted by RitchieD View Post
Newbie. What's the purpose of the capped up-pipe under the sink? Should the cap be on and tight?
Would have helped to see the connections further left, but I'm guessing it is an air admittance valve -- a common way to avoid a through-the-roof plumbing vent stack.
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Old 05-04-2019, 02:38 PM   #4
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Greely, Ontaio, Canada
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Old 05-04-2019, 02:39 PM   #5
RitchieD
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Left pipe is drain for sink
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Old 05-04-2019, 02:58 PM   #6
RitchieD
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more pics. Looks like cap might allow it to breath and i should have it on.
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Old 05-04-2019, 03:34 PM   #7
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Ritchie - here you go...…

https://www.loveyourrv.com/bad-smell-coming-rv-sink/
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Old 05-04-2019, 05:09 PM   #8
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It's an air admittance valve and yes it should be screwed on tight.
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Old 05-04-2019, 07:41 PM   #9
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It's an air admittance valve and yes it should be screwed on tight.
In addition to the above, the air admittance valve has a rubber diaphragm in it that often dries out or distorts and starts to leak "smells" into the camper. They do go bad and they are available at Lowe's or Home Depot. Just take the old one with you so you get the correct pipe size. At Lowe's, they're not in the plumbing section, rather they are in the mobile home repair parts section.
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Old 05-05-2019, 04:44 AM   #10
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John, would a little mineral oil on the rubber seal extend its life span?
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Old 05-05-2019, 05:03 AM   #11
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In addition to the above, the air admittance valve has a rubber diaphragm in it that often dries out or distorts and starts to leak "smells" into the camper. ...
John

I've had a Studor Vent under my S&B kitchen sink for going on 16 years and (knock on wood) have not had an issue with it (maybe because it is used regularly?) Is the Studor Vent design different from the brand typically used in an RV? I know mine has a little ball in it; not sure about a rubber diaphragm.

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Old 05-05-2019, 06:33 AM   #12
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OLIVE OIL....
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Old 05-05-2019, 11:09 AM   #13
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Probably not once it has become problematic. These units are pretty cheap ($5-7) so periodic maintenance is not cost-effective. I've had these last 30 years in manufactured homes before they had to be changed.
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Old 05-05-2019, 08:46 PM   #14
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I think the "reliability issue" with RV use versus S&B use has more to do with extreme conditions the air inlet cap is exposed to in an RV. Between being stored outside in 90F+ temps and -0F temps, the "internals" just don't stand a chance of lasting as long in an RV as they do in a more moderately controlled environment in a S&B.

As for extending the life, I don't know if using some type oil, olive, mineral, Crisco cooking oil or WD40 would work. My guess would be since the device is an "air admittance" function, it "sucks air into the plumbing when you flush or drain the sink. If there's dust/dirt in the air and "sticky oil" on the internals, then that may shorten the life rather than extend it.... So, to answer: Beats the heck out of me if oil would help or hurt......
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Old 05-12-2019, 07:53 AM   #15
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If anything (and I would not use anything) something like a dry lube or silicone would attract much less dust and debris.
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Old 05-12-2019, 08:12 AM   #16
itat
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Here is a very recent video from RVgeeks about that air admittance valve.

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Old 05-12-2019, 09:18 AM   #17
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OLIVE OIL....
Olive oil is great for cooking but not as a lubricant since it will get rancid over time. Canola oil would be better but for something like this I would use silicone gasket/o-ring lube, which I get from swimming pool supply stores (can probably be found at Home Depot, Lowe's or Ace too)
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Old 05-12-2019, 12:29 PM   #18
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Olive oil is great for cooking but not as a lubricant since it will get rancid over time. Canola oil would be better but for something like this I would use silicone gasket/o-ring lube, which I get from swimming pool supply stores (can probably be found at Home Depot, Lowe's or Ace too)
Sorry...I was referring to an old thread on here about lubricating blade valves and toilet ball valves and seals.
It was kind of an old inside joke. Fetus2, our dear departed moderator, and I went back and forth on the subject. It was tons of fun...miss that guy.
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Old 05-12-2019, 01:36 PM   #19
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Sorry...I was referring to an old thread on here about lubricating blade valves and toilet ball valves and seals.
It was kind of an old inside joke. Fetus2, our dear departed moderator, and I went back and forth on the subject. It was tons of fun...miss that guy.
I heard from Festus2's DW a bit ago. She is doing well.

Every time I read a comment about olive oil on the forum, I think about that exchange with Geo, Festus2, you, me and several others. You know, with just the right amount of vinegar (brands do make a difference) we created some awesome "black tank salad dressings"..... I chuckle at some of the recipes, but that's about as far as my "courage" will allow me to go......

Believe it or not, I do pour a little "cheap olive oil" down the toilet trap occasionally. It does seem to help the blade valve to slide a bit easier...... (vinegar optional)
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