Black Tank Odor

[chasfm11]

On our last two trips, we started to experience an odor that seems like it is coming from our black tank when we started to drive. We've had the RV 3 years and put nearly 30K miles on it and have never had this problem before. Admittedly, both time the black tank was registering 2/3 full but we have had it that full in the past without the odor problem.
Here are some facts:
1. About a year and half ago, I discovered that the passenger side of the black tank was not on it's hangers and it was hard to dump. I re-mounted it.
2. I pulled the cap off of the roof vent and ran a snake down the pipe. It goes to the tank without any obstructions.
3. There is a "birds nest" looking pile of a plumber's putty type material around where the vent stack comes into the tank. According to the dealer's tech, GBM uses a rubber gasket to seal the vent stack/tank joint. The plumber's putty like material is very hard and doesn't look easy to remove.

I suspect that there is a seal problem on the vent pipe and that sometime in the 4 years before we owned it, someone did a primitive fix for the problem that has now resurfaced. It wouldn't be easy to drop the black tank or, following the dealer's other suggestion, separate the vent pipe from the roof and pull it up.

Before I started into anything heavy to resolve this problem, I thought I'd see if anyone had any experience in this area. All suggestions (including other possible sources for the odor) are welcome.

Charlie

[chasfm11]

On our last two trips, we started to experience an odor that seems like it is coming from our black tank when we started to drive. We've had the RV 3 years and put nearly 30K miles on it and have never had this problem before. Admittedly, both time the black tank was registering 2/3 full but we have had it that full in the past without the odor problem.
Here are some facts:
1. About a year and half ago, I discovered that the passenger side of the black tank was not on it's hangers and it was hard to dump. I re-mounted it.
2. I pulled the cap off of the roof vent and ran a snake down the pipe. It goes to the tank without any obstructions.
3. There is a "birds nest" looking pile of a plumber's putty type material around where the vent stack comes into the tank. According to the dealer's tech, GBM uses a rubber gasket to seal the vent stack/tank joint. The plumber's putty like material is very hard and doesn't look easy to remove.

I suspect that there is a seal problem on the vent pipe and that sometime in the 4 years before we owned it, someone did a primitive fix for the problem that has now resurfaced. It wouldn't be easy to drop the black tank or, following the dealer's other suggestion, separate the vent pipe from the roof and pull it up.

Before I started into anything heavy to resolve this problem, I thought I'd see if anyone had any experience in this area. All suggestions (including other possible sources for the odor) are welcome.

Charlie

[RV Wizard]

Charlie, a grey tank can smell as bad as a black and there have been occasions where we would loose a "P" trap. I guess the listing of the coach would cause the water to flow out of the "P" trap and allow gas into the coach. When this happens the wife will just run some water down the drains and the smell goes away. You might try this to see if it is black or grey tank odors.

[chasfm11]

Thanks for the suggestion, Mike. I'm going to start pouring water down all of my drains and then putting stoppers in all of them just before I leave the campsite and see what happens from there.

This past weekend, the exit from the campsite was flat and level. We started to get the odor before we got to the entrance of State Park, less than a 1/2 mile away and I doubt that the RV was more than a 1/4 of a bubble off plumb in any direction during that short drive. It could have been than the trap wasn't full before we left and that sure would confirm your diagnosis.

I just don't like the appearance of the stuff around the black tank vent connection. It does appear that it is old plumber's putty and that it might have been put there to help control "spillage" from the vent pipe joint because it feels like there is about 1/2" gap on all sides between the OD of the vent pipe and the inside of the putty stack (which is about 2-3" high). I'm going to try to drop that corner of the tank a little and get either mirrors or my small digital camera up in there to see if I can physically see what is going on.

We are headed out several times over the next several weeks and will get a chance to test the problem repeatedly.

Thanks again.

Charlie

[H. Dossett]

Charlie, I had the problem a few years ago, and then again later. The final solution both times was replacing the floor seal for the SeaLand toilet. It uses a very soft "spongy" seal and it deteriorates pretty fast. Vibrations from rough roads are just one cause of the problem.

Harold

[chasfm11]

Thanks for the input, Harold. I spoke with my dealer yesterday about this problem and the tech never mentioned that seal. We have a Thetford Aqua Magic IV and it looks like there is a closet bolt/seal kit for it so I'll see if I can pick one up. It appears to be a fairly simple change to make and might eliminate the our problem as you suggest.

Charlie

[chasfm11]

Update:
1. All traps were full of water. I blew out the kitchen trap with compressed air and there was no odor. Putting a small fan near the sink in an attempt to pull odors up out of the now empty kitchen trap didn't produce any odors.
2. I removed the cosmetics from around the black tank vent area. It is definitely plumbers putty. Next step is to remove it and see what problem the putty is hiding. I read an article saying that sometimes the vent pipes are pushed too far down into the tank to vent properly when the tank is more than half full. This well might be my issue.

More updates later.

Charlie