It's back....and I'm stumped

[zach477]

Last week I replaced the closet flange seal on my Thetford toilet because I was getting odor in the bathroom when driving or when my fantastic fan was on. At the time it seemed to have worked, but I guess I spoke too soon.

I have plugs in both the bathroom sink and shower drains. The air admittance valve under the sink is brand new and seems to be functioning...no odor under the sink. There is a good 1/2 gallon of water in the toilet bowl.

I'm stumped. I don't know what else to do.

[outofplace]

If its got a washer dryer maybe it is the washer trap went dry thats what was causing our smell issues in our MH early this year

[Old-Biscuit]

New toilet floor flange......no odor thru mechanical seal unless torn or toilet loose
New air admittance valve.....no odor thru mechanical seal (throw a baggie over it to test---turn on exhaust fan HIGH)
Toilet bowl holding water......no odors thru water barrier (unless you can see bubbles churning up thru water)

Vent line........if plugged you would get 'burps' back up thru toilet when flushing and/or black tank would not drain very well

Toilet line to tank (or vent line from tank) may go thru a rubber grommet (gasket) could be allowing odors to come out of black tank and then get pulled up into bathroom thru holes/openings

Or you could have a crack in vent line inside wall and odors are getting pulled into bathroom

[newman_fulltime]

If the fan is over the toilet it has enough vacum that it sucke the oder up through the seal.Close the toilet lid it will help

[fuzzyface]

I had a similar problem -- it turned out that the drain hose from the clothes washer was inserted too far into the 'P' trap, displacing the water in the 'P' trap. I pulled the hose out a little, secured it, and the odor went away.

[rgatijnet1]

What type of vent cover do you have on the roof? Depending on how it is installed, or what is near it, it can be forcing air DOWN the vent pipe as you drive instead of sucking the fumes out of the black tank.

[RV_daytrader]

what model thetford toilet?...on the Aqua magic V, the seal for the flush handle wears and starts to stink.

[DSDP_Don]

What kind of motor home is this? If you put it in your profile, it makes it easier to diagnose problems. Is your coach a single bath or bath and half? Is the toilet located directly over the tank?

Often, if your toilet is right over the tank and water bay, you can get odors coming up from the water bay through plumbing cutouts behind the toilet. Often this area isn't completely sealed.

[korbe]

I would close all the doors, windows & vents and when the odor is strongest, start the smell test and follow it and at least try and narrow the location down.

[gbopp]

Correct, if the vent is clogged air can not get in or out of the vent.
If the vent is not clogged, as you drive the air will be pulled out of the black tank.

You notice the smell while driving or, when the fan is running.
Possibly something is blocking the vent that acts as a one way valve? Air can get in the vent but, not out.

Driving or running the fan causes a slight vacuum in the tank and the smell is possibly seeping out around the rubber seal on the toilet. Try resetting or replacing the rubber seal, maybe it's not seated correctly?
But I would start with checking the roof vent.

That's all the physics I can offer. 🙂

[zach477]

To those suggesting it's the air admittance valve, I stated in my original post that it is brand new and functioning correctly. There is NO oder under coming from under the sink.

I have not yet checked the vent on the roof. Just looking at the physics of this, it seems that if it was clogged, air couldn't get in. If air can't get in through the vent on the roof, how could my fantastic fan pull air into the RV from the black/grey tanks? You can't pull air through a straw if your finger is on the other end. 😕

[midnightsadie]

I had this too and it turned out to be the slide seal was leaking ,yet it would hold water. don,t no how ,but changed the slide seal and it was fixed.

[Trackrig]

Recently, each time we drove the MH, after about 10 miles we'd get a strong sewer smell also. Figured out it had to be one of the sink drain line vents that weren't venting properly. After doing some reading, the mfgs recommend changing them out every ten year - our were about eleven years old. Changed all three since I wasn't sure which one was the problem. No more odders.

I first went to Home Depot and bought three of them. Went back to the MH and got two of them installed. On the third one, it was right up against the sink and the ones from HD were too large of a diameter to install. It took a while, but I finally found some at an RV place that had the same small diameter as the original ones.

Look in the picture just to the right of the sink at the top of the black plastic pipe - that's your vent valve. Just unscrew.



Bill

[enblethen]

Look under the bath sink for a vacuum check above the P trap. If it is weak, fumes can be sucked into rig.
Air admittance vent

[gbopp]

Did you make sure your black tank vent on the roof is not clogged?