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Old 07-08-2016, 02:18 AM   #1
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Default This is why your toilet stinks

There was a thread a few months ago regarding the install of one of those vent caps that sucks fumes out of the black tank to reduce odors in the RV. An astute reader pointed out that if the toilet is sealed there should be no way for gasses from the black tank to get in to the interior no matter what was going on with the vent. This line of thought assumes that the toilet is actually sealed like a toilet in a regular house which is not always the case.

The venerable Aqua Magic IV that is installed in so many class B rigs is not built the way you may expect. The bowl sits in the outer housing which acts as a big funnel and when the drain flap opens it drops the load of waste in to that funnel which in turn is attached to the drain. There is no connection between the bottom of the bowl and the drain. This means that there are plenty of opportunities for gases to escape and one in particular is enough of a problem that Thetford actually did something about it.

On older (I don't know how old) Aqua Magic IV toilets there is an overflow opening right under the water outlet. The overflow opening is attached to a tube that is bent in an "S" shape to act as a trap and that tube drains in to the base of the toilet right next to the flapper mechanism. The idea was that if the toilet was overfilled that water would drain down that hose in to the black tank. This means that after a few road bumps or the proper draft that causes that tube to be empty of water that there is an open black tank vent in your bathroom. Thetford eventually figured this out and the parts diagram shows that tube is no longer available. My understanding is that they recommend blocking the opening instead of replacing the tube if it needs to be repaired.

Here is a picture of the insides of the toilet showing the stink tube. Notice the putty or caulk in the groove where the top assembly seals to the base. The picture is grabbed from this YouTube video-

AquaMagicIV-Innards.jpg

If you open the toilet lid and look on the left under the water outlet you can see the stink hole.

AquaMagicIV-OverflowTube.jpg

Theoretically some water drips down in to the tube to keep the trap full when the toilet is flushed but in reality that doesn't happen very well and S traps are prone to siphoning as discussed here- A Primer on "S" Traps Structure Tech Home Inspections.

If your toilet has the stink hole/tube go ahead and fill it with silicone or something. Your significant other will thank you.
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Old 07-08-2016, 02:49 AM   #2
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Old 07-08-2016, 04:31 PM   #3
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Thanks BBQ! That is a great video. Now I'm going to use petroleum jelly as preventive maintenance to prolong the life of the toilet seal.
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Old 07-08-2016, 04:32 PM   #4
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Thanks BBQ! That is a great video. Now I'm going to use petroleum jelly as preventive maintenance to prolong the life of the toilet seal.
Silicone grease is even better.
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Old 07-08-2016, 04:52 PM   #5
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Silicone grease is even better.
A LOT better, actually. Vaseline, I am told, attacks many kinds of rubber.
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Old 07-08-2016, 06:09 PM   #6
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Not sure about needing the q-tip, if you have a disposable glove on why not just put some on your finger and apply it around the seal. Seems easy enough to me...
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Old 07-08-2016, 06:36 PM   #7
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Default For the times when the bowl seal is _not_ leaking

There are times that even when the flange seal is not leaking and the bowl seal is not leaking the toilets will still vent and stink due to the aforementioned overflow tube. Of course all sources of leaks and black tank fumes should be investigated.
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Old 07-08-2016, 07:48 PM   #8
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Every RV should have one

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Old 07-09-2016, 01:30 AM   #9
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Old 07-15-2016, 11:25 AM   #10
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How complicated is it to replace the whole thing with a compost toilet?
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Old 07-15-2016, 02:01 PM   #11
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How complicated is it to replace the whole thing with a compost toilet?
To replace it with composite is not difficult,

but composite is not the solution to everyone's situation.

if it were, then there would not be other types of toilets.

The first consideration is the cost. You are looking at $1,000+ on the toilet alone.

Then you have to find places in your crammed RV for moss or coconut shell.

The liquid container is small; you pretty well have to dump it every other day.

The composting does not work if you have too much or too little waste.

Some people dump the waste in the garbage, which can cause problems to the community.

...


not insurmountable problems, just like any other types.
Different strokes for different folks.
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Old 07-15-2016, 02:18 PM   #12
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If you use coconut fiber it comes in compressed blocks that don't take up much space, you add water to rehydrate it and it expands for use. Here is the Wynns video showing how it's done...

How to Prep and Dump a Composting Toilet
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Old 07-15-2016, 02:28 PM   #13
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Originally Posted by gregmchugh View Post
If you use coconut fiber it comes in compressed blocks that don't take up much space, you add water to rehydrate it and it expands for use. Here is the Wynns video showing how it's done...

How to Prep and Dump a Composting Toilet
Hey... if I have Wynne's 120' Class A, I would have not storage problems either.


just kidding... I agree, the coconut do not really take up a lot of space.
If you are boondocking, you can dig some dirt and they work the same.
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Old 07-15-2016, 03:05 PM   #14
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Thanks for the reply s. ..is there anyone who has done this in a road trek 190 pop.?
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Old 07-15-2016, 03:09 PM   #15
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Thanks for the reply s. ..is there anyone who has done this in a road trek 190 pop.?
Yes. There is a woman living in the desert using one.
Not sure if it is a RT190, but it is a class B.
I will try to find the vid for you.
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Old 07-15-2016, 03:15 PM   #16
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Thanks, I asked Bob..The one who interviewed her....said he would get back to me if she started ablog? How do I get in touch with her....????
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Old 07-15-2016, 03:17 PM   #17
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Thanks, I asked Bob..The one who interviewed her....said he would get back to me if she started ablog? How do I get in touch with her....????
There are more than one lady doing it...

here's one.

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Old 07-15-2016, 06:25 PM   #18
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Default Success!

I plugged the overflow tube with a slice of a synthetic wine cork before our most recent trip. After a couple thousand miles I can say it made all the difference. If you have a overflow tube none of the common remedies will completely get rid of the odors without plugging the stink tube.
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