[Archived]

It has been a few decades since I took an air admittance valve apart but my memory seems to recall it is essentially a check valve. A ball is held in the seated position (closed) by a light spring. When water is drained in the sink for example it needs air behind it to keep flowing so the slight negative pressure within the piping between the water flow and the air admittance valve causes the device to open, allowing air to enter the vent system. When the flow of water stops the ball reseats itself.

[Walter]

Yes, as Jon said. They allow air to go into the pipe but are not supposed to allow air to come OUT of the pipe. They are a solution to the problem of running pipes to the roof.

The original ones had a spring and a flat piece of rubber. But the new ones were just a rubber flap. The 26$ ones you can’t actually see how they operate.

If you stick it to your mouth (a new one please!) and blow you can’t blow out of it. I think they have to be sort of delicate for them to really work effectively. Probably why if not made right they don’t work.

I still don’t really get how the cheaper one didn’t stop the flow of air out of the grey tank when I tested them with the fantastic fan. But maybe they have manufacturing problems. I only blew into 1 of them. I don’t know which one. But installed 3.

Walt

[Archived]

Just replaced all four mine today and definitely makes a difference!

Since the black tank is vented thru the roof, I’m assuming there is no check-valve necessary since the gases simply go up thru the roof like a residential home.

[Peter]

I don’t know if you fixed the problem or not but just for info if it is still happening the easy fix is to run your clothes washer at least once a week. Believe it or not.

H Marathon

[Corey]

Walt

thank you for posting this thread. I have been battling the dreaded stink for awhile now. I replaced the old ones multiple times. No stink for a few days then it returns. I was putting in the $5 cheap ones. I also pulled

the microphor toilet and sealed the mount plate and put in a new seal. I also did some fixes the toilet needed while i had it out. New hopper seal, flapper arm, etc

Now that i have read your post, i went to Lowes and bought 3 of the Studors. I don’t need 4 as we pulled the washer & dryer and capped the system last summer.

The first 2 installs were easy. Both units under the vanities were easy unscrews and replacements. The one untder the galley sink is another story. CC installed a 4 inch wide by 1/4 inch crossbrace in the back of the sink area. They have the sink plumbing running to the wall and down. The airator rises behind the brace. Needless to say, the Studor will not fit. The old airerator barley screws in. The brace and the side of the bus leave a wee gap. Just enough room for the old style.

i will need to cut a notch out of the brace. In order to try to keep its strength, i will add a 2 inch wide by 1/2 inch wide 10 inch long piece to the brace. I am hoping this will provide stiffness to the brace to make up for the notch. This will be next weekends project.

If it works, i am hoping the stink will finnaly be gone. Thank you for posting about the Studors.

[Chuck]

My point was you do not have to replace anything, just run the washer once a week clothes or not and you won’t have an odor from anywhere. It works try it before you spend the money.

[Corey]

Good tip on the washer, the P trap goes dry.

[Peter]

In our bus, I could open the door the the bathroom sink vanity and WHOOF! Smell that would hit me in the face! The washer vent would be on the bedroom vanity and kitchen sink side (on our bus at least) But for sure…. run the washer too because…

I don’t 100% recall when looking at the washer drain pipes, but these vents should be installed after a p-trap. So… you need to do both. Good vents and full p-traps.

We actively use our bus all the time so we end up running the washer regularly and basically use everything regularly. I haven’t had a smell problem since the upgrade. Fingers crossed!

[needtocamp]

once in awhile the vent pipe on the roof can get a crack in it below the roof and travel inside the ceiling and come out inside coach , it gets cracked because someone hit a tree branch, so check that also, you can not see the crack from the outside on the roof unless you take the vent cap and cover off and can look down inside coach

[DON]

Interesting Peter,

Didn’t know that vent pipe could crack, but another great tip if I experience smell from the toilet vent area.

[Chip & Pam]

My old beast doesn’t have any holding tank odor EVER. GoneCrazy & Dick in Wisc what say you?

Mine has one vent on the roof. That’s all.

[Archived]

I have an RV toilet, you flush you see into the tank. I found that even with water in the bowl I would get a smell. In searching I found that the two holes just inside the rim were the source. I now fill those holes with water like a p- trap and I am good.

[Andre]

There is one air admittance valve on my coach i have not found. It is the one tied to the shower drain. Does anyone have a vintage Xl from country coach? If so, is the air admittance behind & near the soap holder insert in the shower? Or is it near the cubby next to the shower?

I’m trying to find its location before i tear into stuff.

[Peter]

I’m just gonna ask/say – do we even “need’ vents on these buses?

As far as I know… a vent would allow air IN to the system when you have a water flow down the drain that “fills up the drain diameter and woud go down very slowly in that situaion. On a regular house, the ven would allow a surge of air/gas from the serwer system to go out the ven and hopefully leave your P trap full of water.

On our busses – the cheater valve won’t solve problem #2. Only problem #1… but I and wondering is problem #1 really a problem??

[Dan]

after doing some research, i found in a manual a schematic of my plumbing. I have a drain line running from my shower p-trap to the grey tank. It is about 2 feet from the trap to a sideways T fitting. The top of the T goes up to an air admittance, the bottom of the T feeds the grey tank. The horizontal part of the T runs to the ptrap.That is it. The air admittance is behind the bathroom wall along with a vent from the grey & black, those vents tie together and out the roof vent.

since i cannot get to the air admittance valve & the fact that it is 18 years old, i am left with one option. I can cut the line, remove the T, and run a 90 from the ptrap line to the grey. I can then cap the verticle line which has the air admittance valve.

Q: why would they have a air admittance on a 2 foot run? I don’t get it. The darn grey vent pipe is 6 inches away from where the T. connects to the tank.

im attaching a picture of the schematic. line 2 is the shower drain. Any thoughts?