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.

[lonfu]

Ok, so ran into something similar with my MIL moho. She had a factory installed black water tank wash out option. What does this have to do with smell in the bathroom? Turns out that there is a check valve, under her bathroom sink that is above the level of the black water tank that keeps the wash water from back flowing into one's clean water system. When MIL's valve got stuck open, it vented black water gas into the bathroom. It is a check valve that allows water flow one way and then vents to the air to allow drainage. If it sticks open it will allow venting directly to the bathroom of the black water stink. Went through the toilet seal thing and tank vent thing too......

[dieharder]

nemo45 wrote:

dieharder wrote:
When the fan is on, or if you're driving down the road with the roof vent open, you're creating a low pressure zone in your bathroom. It could be pulling air up from the tank through a leaky seal between the toilet and the tank and have nothing to do with the flush/flapper seal at all.

If you have your fantastic fan or the bathroom fan on and you flush the toilet it will draw odor up thru the open vslve in the toilet bowl, leaky seal or not. There's nothing you can do about that but shut off the fans when you flush. And really, closing the toilet lid under those circumstances isn't a bad idea. Putting a Tee or the venturi type that swivels will definitely help will going down the road or anytime its windy. But if I have my fantastic fan on in the bedroom and the bedroom window open and the toilet is flushed it will draw the odor in thru the window.

Considering that the OP indicated when driving or the fan is on, I think it's fair to assume that he's not talking about 'when flushing'. If he's getting odor just when the fan is on, then it's probably pulling the smell up through a leaky seal, and not just the one in the bowl itself, as I indicated.

[catkins]

Hoping you found the odor. We had nasty odor and turned out to be the GREY tank. When P traps were empty we would get a terrible smell while driving. Had the tanks cleaned professionally(RV Proctologist style) with high pressure internal sprayer, and grey tank was nasty. I now occasionally put chemicals in the grey tank to biodegrade when parked So far so good.

Hoping you resolved your issue!

[nemo45]

dieharder wrote:
When the fan is on, or if you're driving down the road with the roof vent open, you're creating a low pressure zone in your bathroom. It could be pulling air up from the tank through a leaky seal between the toilet and the tank and have nothing to do with the flush/flapper seal at all.

If you have your fantastic fan or the bathroom fan on and you flush the toilet it will draw odor up thru the open vslve in the toilet bowl, leaky seal or not. There's nothing you can do about that but shut off the fans when you flush. And really, closing the toilet lid under those circumstances isn't a bad idea. Putting a Tee or the venturi type that swivels will definitely help will going down the road or anytime its windy. But if I have my fantastic fan on in the bedroom and the bedroom window open and the toilet is flushed it will draw the odor in thru the window.

[dieharder]

When the fan is on, or if you're driving down the road with the roof vent open, you're creating a low pressure zone in your bathroom. It could be pulling air up from the tank through a leaky seal between the toilet and the tank and have nothing to do with the flush/flapper seal at all.

[Tinstar]

Mine developed an odor and after trying several things I found out the vent pipe was not secured to the black tank. Air was leaking between the tank and the vent pipe. Luckily, I was able to get to where the seal was so I was able to seal it myself.

[zach477]

dougrainer wrote:
Did you do the which tank test I outlined to do????? Are you POSITIVE it is a Black tank odor? One thing that can happen is, the down flange pipe to the top of the black tank can break loose. That will allow the debris to go in the tank, but odors will escape past this break. The only way to check is to pull the toilet and remove the down flange/pipe. Also, some RV's do NOT have a threaded pipe going in the top of the black tank. They have a rubber slip ring and if that rubber has deteriorated he 3 inch down pipe will not be vapor sealed. Last, NEVER TAKE ADVICE FROM A PARTS PERSON, what would they know? Doug

Kind of. I actually put a bunch of Lemon oil in the black tank. So pretty much the same effect. I've also put a baggie over the AAV under the sink and plugs in the drain.

I've taken the toilet off and replaced the flange. I didn't check the pipe that closely, though. That could be what it is. 😕

[Ozlander]

Vent caps do nothing for odors when the fan is running.

[dougrainer]

Did you do the which tank test I outlined to do????? Are you POSITIVE it is a Black tank odor? One thing that can happen is, the down flange pipe to the top of the black tank can break loose. That will allow the debris to go in the tank, but odors will escape past this break. The only way to check is to pull the toilet and remove the down flange/pipe. Also, some RV's do NOT have a threaded pipe going in the top of the black tank. They have a rubber slip ring and if that rubber has deteriorated he 3 inch down pipe will not be vapor sealed. Last, NEVER TAKE ADVICE FROM A PARTS PERSON, what would they know? Doug

[zach477]

Not much of an update yet. One of these days, I'm going to get up on the roof to give it a good cleaning and inspection, and then I'll put a new vent cover on, maybe the cyclone, and see if that makes a difference. If that doesn't work I might just replace the toilet. I've been wanting one with a foot lever instead of the hand flush anyway. 😉

[Gary_]

For what its worth we used to get the black tank oder when driving down the highway. We found out that we had it when we had the ceiling vent open in the bathroom while going down the road.
When we close the ceiling vent we do not get the smell. It almost seems like the vent would suck fumes inside while under way. We now close that vent and no longer have any problems. Good Luck.

[lonfu]

So, where is the stinking update? Did you replace the pot or did you duck tape it over and now use a coffee can with a lid?

[barmcd]

vance wrote:
Other people have had this problem including myself. The easiest way that I found that cured mine was to buy the venturi directional vent and install one on each tank (grey and black)vent.

My 2000 vintage coach came with one of those. THE PO said it was the only way to get rid of the smell from the gray tank.

[lonfu]

Jim & Betty wrote:
OK I will take a shot at it a couple of thoughts from past experience from me and others.

You have a leak in the tank black or grey leaking into the sub floor. Co-worker had that problem.
The vent pipe is or has been pulled from the tank black or grey and is now venting into the sub floor.
The vent pipe is too short or was put together in more than one piece and that joint has come loose allowing gases into the wall or sub floor.
You have a vent issue where the tank pressurizes like an odd shaped tank where the levels in the tank block the vent causing the tank to pressurize. This happened to me I had grey water blow back through the bath sink.
You have a rotten potatoe in the pantry. :B
Your hot water tank has stagnated and is putting out hydrogen sulfide that does stink, long shot here because you do use the hot with the shower, assuming.
A battery that is going south will also smell up the place.
You have a dead animal in the heater vent at the bathroom

Good Luck
JimR

I'd like to add to this list,

Did some one take a leak in your shower when they were drunk?

Do you keep your dirty cloths in your bathroom?

Did you check your toilet down pipe by blowing into it? Let me know when you are going to do this so I can come watch, with gas mask in hand (-:........

Just had to get that off my chest! Seriously, all RV toilets have what is called a bowl vacuum breaker valve. Most of the time they are located internally inside the bowl structure to prevent, when opening up the (poop)drop valve, a big blow back into the coach and onto some ones bare bottom. They are not serviceable. The only way to repair them is to replace the entire toilet. Hard to guess how long they will last, use it more perhaps it will last longer or it may just wear it out! When I used ours less it failed in just a couple of years, when we lived full time it lasted 10 almost 11 years. Who knows the life of a toilet vacuum breaker valve until one can smell it! Nothing worse than making coffee in the morning and the smell of ones toilet be stronger than fresh brewed coffee!

Most of the time these valves are just little pieces of rubber laying over an opening. The opening or the flapper grows mold on it and fails to seal out the black tank smells. Yes, I know, no one likes to buy a brand new toilet, but some times you just have to bite the bullet and do it or tolerate that wonderful early morning smell when you first wake up that is not the wife's breath!!!!