Malodorous Motorhome

[karls]

Our '98 24' RB has an interior black tank stink that defies location.

Here's what I've tried.

Replaced commode and floor to commode gasket. Commode flush door water seal is good and it holds water.

Using the blowing side of a shop vac, and after sealing all four sink traps I blew plummers smoke in the roof vent. No smoke came out inside the coach.

The problem is associated with the roof "stink pipe" vent, because when it is intentionally plugged with a rag the odor ceases. This must be because there is a reverse flow when the coach windows are open and there is low pressure inside the coach.

Any ideas out there?

Thanks in advance!

Karl

[randallrae]

We found that some of sink traps would loose water while traveling and the coach would start to smell . Stoppers in the drains help block the odors . The present coach has one sink that drains to the black tank !

[David and Susan Bratt]

We rarely use our shower and find that we must make sure there is water in that drain.

[karls]

The grey and black vent systems are completely independent in our '98 RB. The odor is definitely of black tank origin, although we never use the toilet for "#2".

As suggested, I've ordered two venturi-style roof vent caps that claim to create a low pressure with any air movement.

Also, since the tank has never been cleaned I'll do that and keep adding pure water when we use the coach - another frequent suggestion on forums.

And I'll try the plummer's smoke bomb again. They only burn about 30 seconds and with the 20 feet of hose and vent pipe between the shop vac and the commode it may be that that smoke never made it to the leak (which is probably quite small).

What we need is something akin to a drug-sniffing dog, only one trained to home in on about the same aroma they seem attracted to in dog social world!

[karls]

Sam,

One part of the attempt to stop the odor was replacing the Thetford round rubber gasket with a standard wax seal used on most household commodes. It seals fine, but requires some cleanup and a new seal every time you remove the throne.

Karl

[jlef123]

A motorhome is not stationary like a brick and mortar home. I would think you would be concerned that as you drove down the road and the coach shaked'rattlled' and rolled that the home style wax seal will eventually fall apart and you will be left with no seal for the toilet. There is probably a good reason why the Thetford engineers choose a rubber seal instead of wax.

[randallrae]

1998 owners manual shows 24rb bath sink drains to black tank , and possibly both tank vents being connected , and an anti siphon vent on the bath sink drain .

[karls]

The wax seal is more flexible than the original rubber ring and won't dry out and shrink like it did, and the two hold down bolts for the toilet ensure that there is no play between the toilet and the floor. The only downside is the minor inconvenience of removing all the wax that remains behind when the toilet is removed - hopefully not often. But it's not a nasty job and requires less than a minute. The nice part about the job compared to a household toilet removal is that the RV units are much lighter and easier to position correctly.

The bath sink does drain into the black tank and that pipe T's up to the roof vent, thus providing a vent for the black tank. And my manual does show an anti-siphon valve, but none is installed that I could find.

If plan B does not work (venturi vents on the roof), plan C will be to install a 12V computer fan in the vent system.

Thanks for the input. BF Group is a great resource! And so is Kim!!

[Mel Wilbur]

Karl, if you want to power vent the system you might want to check this out http://www.lslproducts.net/IL-DSPage.html

[Mike Astley]

Karl,

Wondering if your Born Free's toilet is the same as mine (plastic moulded Thetford) if you would be willing to share with me the gasket and seal parts numbers you replaced on your toilet?

My Thetford will not hold water and I am wondering what the fix will be. Is it going to be the black rubber seal you can see from up above that interfaces with the knifeblade sliding trap door, or is it just a matter of tightening a couple screws, but where, and how to get to the rubber O-Ring seal?

I found a packet of several rubber kit gasket/O-Rings at Camping World, but the floor sales rep didn't know if it would be the ones I needed for my Thetford.

Thanks, for any help!

Sam,

There is a video by a fellow Born Free'r documenting the gaskets needed and the replacement process:

https://www.youtube.com/watch?v=6wRBf2_BuMg

I did this on our toilet this last winter. The hardest part was cleaning off the many years of nasty gunk that has built up on the inside. Also be advised that at times when he says something is a "little difficult" it tended to be really difficult for me. Also a couple of times I needed another set of hands to complete a task.

But, all in all, it's doable and you end up with a toilet in great shape.

I should add that you only want to take this on when you have done all you can to clean the knife valve gasket from debris or calcium deposits that are stopping it from sealing, as cleaning the gasket is much easier than replacing it.

[Mike Astley]

With some water in the toilet, drop a small drop of food coloring into the water. It will often reveal where there water is draining from. Then you can concentrate your cleaning to that spot.

Also, if cleaning attempts fail, I got it to stop for one summer by applying plumbers grease to the leak spot.

[karls]

Before installing the new toilet I cleaned the groove the blade slides into with a piece of wire coat hanger with a 90 degree bend at the end. A bunch of old tp was cleaned out but the water still seeped out of the bowl after a couple hours. That's not a big enough leak to cause the odor problem we occasionally have, but I replaced the toilet anyway due to corrosion and a leaking supply line at the foot pedal.

The seal replacement I mentioned earlier is not the one at the bottom of the bowl that the knife blade seats into. I replaced the toilet to floor gasket with a standard household wax gasket, thus replacing the original round rubber ring gasket.

I'm in the process of replacing the original roof vent with a siphoning style from 360 products. A complication just noted is that the original vent is installed on the curve of the roof, and the new vent can not be distorted to fit as was done by BF. Looks like I'll be fashioning a curved spacer.