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Old 08-07-2015, 08:05 PM   #1
Join Date: Mar 2015
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Sewer Smell in bathroom

Folks, I am at my wits end and need some help. I have a sewer smell in the bathroom of our 2012 Wildcat 322RK. The last two times we have gone camping the smell will start after about three days. Here is what I have done and I am running out of ideas.
After first trip, I removed toilet from camper and cleaned it top and bottom. It is the Dometic 310 not the 300 that was a bad toilet.
Replaced the vacuum breaker on the toilet that is behind the seat.
Replaced the vacuum breaker on the black tank cleaning shower.
Repeadly dumped, flusher, and showered black storage tank.
Caulked between toilet anfd floor.
Checked vent on top and did not see anything wrong.
Put treatment in tank after flushing.
I am running out of ideas and am getting very discouraged. Any othe rideas or suggestions would be greatly appreciated.


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Old 08-08-2015, 06:05 AM   #2
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Have you check for a defective air admittance valve underneath bathroom sink? Sometimes smell come from grey tank.
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Old 08-08-2015, 06:28 AM   #3
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I found the one dose of tank stuff (whatever you use) is not enough. I double the dosage for my tank but I have a large black water tank. I also found that the green environment stuff is worthless.
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Old 08-08-2015, 06:31 AM   #4
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"the smell will start after about three days"

It's hot out there. Why not just dump it the third day.
Are you keeping some water in the toilet bowl all the time?
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Old 08-08-2015, 06:31 AM   #5
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You do not state where you are located. In hot weather things ferment quicker than in mild temps which is obvious. Add additional odor control products or dump in two days instead of three.
It sounds like you have covered all the bases as far as venting ect. You didn't happen to drill a hole through the wall into the vent pipe to hang a towel rack or something did you?
I dump after every weekend trip, use odor control products and tissue desolver without issues.
Is this 2012 wildcat new to you or did you buy it brand new and this issue just started?
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Old 08-08-2015, 06:42 AM   #6
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The problem is your air admittance valve under your sink. The cheap black ones used by all RV manufacturers fail way before a good one will.

Remove the black air admittance valve by turning it counter clockwise, then install a new 1-1/2" air admittance valve. There are several brands, but Studor Vent is the most used in the residential plumbing industry. You can also find them made by Oatey, ProFlo and others. Do not buy another cheap one. You should be spending about $20.00 on a good one.

This is going to fix your problem.

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Old 08-08-2015, 06:59 AM   #7
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if you have a Dometic 300 toilet, that may be your problem. They had a long run of bad ones that create a smell. I had one.
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Old 08-08-2015, 07:07 AM   #8
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I had the same problem with my Sabre 5th wheel.It turned out to be the HepvO valve which is located in the sub basement. After plugging up twice I replaced it with a P trap.
Here is a link to them [URL="" .
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Old 08-08-2015, 07:15 AM   #9
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Try This put some Dawn Dish soap down the toilet along with a bucket of hot water, if there is anything built up in there it will loosen it up. Let it sit for an hour or so then put a wand tank cleaner down and flush tank good. I tried using the Dawn and calgon to sanitize our tank and it did work but if there is build up nothing seems to work. If you can take the trailer down the road with the hot water and Dawn mixture in the tank the sloshing around will help with the cleaning.
Think about things before you do them make life easier not harder.
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Old 08-08-2015, 07:28 AM   #10
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One more idea. If you are not using the shower, the water in the trap can evaporate or be sucked out during dumping. Try pouring 2 cups of water down the shower drain once you set up.


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