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Old 08-08-2016, 05:51 AM   #1
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Sewer Odor While Showering

When showering, there is a strong sewer smell. The gray tank is closed and I am puzzled as to where this odor is coming from. Last night while washing dishes I noticed a faint sewer smell too. The mh is a new, 2017 Fleetwood Bounder that I bought 2 months ago. I have checked the vents under all the sinks and they appear to be working properly and closed when no water is flowing. I expect there is a check vent on the shower too, but have no idea where it is or how to access the P trap area. Any help would be appreciated.

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Old 08-08-2016, 05:55 AM   #2
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Did you have a fan running. I notice with ours sometimes when one of the fans or the AC is on and you flush the toilet it will bring some of the odor in the tank up into the RV. If you have a washer hookup make sure it is capped or there is water in the trap. I like to just cap it as water will evaporate in the trap.

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Old 08-08-2016, 06:09 AM   #3
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We have been parked for the last 20 + days and have also experienced the same mentioned smells. The other day I smelled it while the bath vent fan was sucking moisture from the bath area. So I thought it was the fan. Then later I smelled it when the fan was not running. The DW has smelled it from the kitchen sink area as well.

I'm almost positive the smell is coming from the GRAY and not the BLACK tanks. While both tanks will smell I'm sure the black tank is much worse.

I have smelled the black tank when running the fan in the bath and flushing the toilet. That's definitely a much worse odor as one would expect. The odor we are smelling is just slightly bad so it has to be the gray tank.

We all know about the P-traps. There are P-traps in all the water areas: below the shower, rear sink and kitchen sink. That is the U shaped tube which holds water. It is supposed to keep smells below and in the gray tank.

There are also roof vents that are suppose to allow the gases to vent keeping the odors away from us and the tanks pressures down. They are drawn away by wind very much the same as what happens on the roofs of all homes.

Here's a guess. When the gray tank produces odors because of bacteria action as the pressures increase they have to get out. If the roof vent is temporarily obstructed by wind gusts into the top of the vent tube on the roof the pressure in the tank may build and escape through the water in the P trap below one of the coach drains: bath sink, shower, or kitchen sink.

Since this does not happen all the time I'm also guessing it occurs when a drain is being used. When one of the sinks, or shower are draining the water is flowing through the P trap and because of it's natural tendency to swirl as it goes down it may be providing a temporary opening and some the gases escape back up the drain.

There is a roof vent that is supposed to work better than the standard vent. It is a directional vent and will swing so the wind will not allow air pressure to upset the balance of pressures and allow the tank properly vent.

I can't remember the name of the vent but they are not expensive and can easily be installed. I think I'll do some research and see what i can find.

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Old 08-08-2016, 07:25 AM   #4
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The fan is not running when the odor is present. I understand about the P trap & it's function, and agree. However, this odor started the second weekend after I bought the mh, which was the he third night staying in it. I have filled the gray tank over half full and added a packet designed for the gray tank with no success in cleaning it out. I am beginning to think the tank vent system is leaking gases on the way to the roof. Still searching. Thanks for the responses.
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Old 08-08-2016, 07:35 AM   #5
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TeJay might have meant the Cyclone sewer vent?

If you want to catch a leak fill the gray tank by running the shower until overflow (in the shower). Keep an eye out. If you are successful filling up to above the shower drain then there is no air leak from under that level and you most likely have a vent issue.

Maybe vent is blocked, maybe run a hose to roof and run water down the vent.
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Old 08-08-2016, 07:52 AM   #6
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I installed two of these and eliminated almost all odors. With just a little bit of wind blowing across the top of the RV you can't smell the black tank even with the toilet bowl flapper held open.

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Old 08-08-2016, 08:26 AM   #7
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AAV - air admittance valves. These are mounted under every sink because as water flows down a drain, it needs to have air behind it - otherwise it goes glug-glug-glug. Your house vents the sinks into the roof vent stack; your motorhome uses an AAV to accomplish the same thing. Go to your local hardware store and pick up some new ones, about $20 ea., and replace the cheap ones used by your motorhome builder.
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Old 08-08-2016, 08:38 AM   #8
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Thanks Roger, but how about the shower? That is what produces the worst smell when in use. I don't know where that one is located.
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Old 08-08-2016, 08:57 AM   #9
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First thing to look at is the AAV or static vent under the sink. These are well know for leaking. As a temporary fix, you can put a wrap of tape around it to see if that is the smell source.

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Old 08-08-2016, 09:03 AM   #10
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The air admittance valves will be under the kitchen sink and each bathroom sink. The are(should be) installed snuggly by hand and can be purchased at most big box stores. The following link is an example od where and they are "reasonably" priced. Consider replacing yours and keep a couple on hand for spares. Putting the whirly gig type spinners on each roof vent should be considered also.

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Old 08-08-2016, 02:15 PM   #11
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Would anyone like to hazard a guess as to where the AAV might be for the shower? That is the one I can't find to check.
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Old 08-08-2016, 02:57 PM   #12
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Originally Posted by Fchandler3 View Post
Would anyone like to hazard a guess as to where the AAV might be for the shower? That is the one I can't find to check.
The shower may use the same one as the sink. I think the plumbing code is a vent pipe (or AAV) must be within three feet of the drain. If you shower is close to the sink, then they could be sharing one.
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Old 08-08-2016, 03:02 PM   #13
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I believe they don't have one. I don't believe it has an s trap either.
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Old 08-08-2016, 03:19 PM   #14
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Originally Posted by cwit View Post
I believe they don't have one. I don't believe it has an s trap either.
What are "they"?..
What is the "one" they "don't have"?
And what is a "s trap"?

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