holding tank smell

[DennisB]

Hi-have a 2020 Trailmanor and have owned it for just over a year now. After our last trip in early June, I parked the trailer in the driveway, emptied both gray and blackwater tanks, flushed them then drained them again. I put some deodorant
in the blackwater tank and it has sat. I should explain that we chose to have a thereford toilet with built in holding tank installed rather than the recirculating toilet. This toilet sits right on top of its own holding tank and then is plumbed from below tying into the normal sewer line outside the trailer.

Anyway, after a few weeks of sitting, the trailer started to smell and got increasingly worse. I flushed both tanks again, hosed out the inside of the toilet holding tank so it looks really clean, then filled both tanks with "Thetford Tank Blaster".
as per the directions, I let is sit overnight and then drained and flushed both tanks the next day and the results were good-no smell. Everything was fine for about 10 days then it started to stink again. A slight smell in the morning then increasingly worse as the day progressed. I have drained and applied the "Tank Blaster" treatment again and am awaiting the results in the morning.

No one is using the trailer's sink or toilets during this time-
As mentioned above, the toilet tank is really clean and it sits right under the toilet itself so I can literally stick my nose in there and it does not smell bad.

I suspect all the smell is coming from the gray water tank and I am looking for a solution. Its wierd because we have used this trailer frequently for the past year and have had NO problem like this before-
I am wondering if I need to pull the gray water tank and replace it--

Any suggestions/advice would be appreciated-
thanks,
Dennis

[Bill]

Pulling and replacing the gray water tank would be surprisingly difficult and expensive. I suggest you put that at the bottom of your "try this" list.

On the forward wall of the tool compartment, there is a removable panel. If you remove that panel, you have access to the plumbing under and around the tub. Have you removed that panel and sniffed around in there? Is anything wet in there? Have you looked around with a flashlight and a mirror?

My other thought is that a small animal (mouse?) somehow got into the plumbing system, or into that back plumbing area, and is decomposing there. I don't know how to check inside the tank, except to get yourself a borescope camera (not expensive) and examine the inside of the tank, as well as the hard-to-reach areas of that plumbing area.

Bill

[DennisB]

Hey Bill, thanks for your reply. I have checked that little door inside the back hatch. I can see into that area pretty far and there is no wetness I can see.
In the past there has been a little odor in that area, but I believe the bathroom fan vents into there--is that correct?

As far as a small rodent, I don't think that is the answer-this afternoon, after I filled and treated the tanks with Thetford "Tank Blaster", the odor has disappeared. I don't know if this is because the tanks are full or not-but if it was a dead rodent, the smell would have remained--tomorrow, I will drain the tanks and see what happens.

I will have to keep working on this, try different chemicals etc. Its just weird that for a year, I have had no problem and now suddenly I can't keep the odor from coming back.

thanks again-

Dennis

[Shane826]

I think this is your toilet? Dometic SeaLand Traveller. It’s a very popular upgrade. You got one of the unicorns that came with that directly from the factory!

As for your gray tank stink, are your drain p-traps dried out? Pour a gallon or so of water into each drain (2 sinks, bathtub). Having water in the p-trap should block any odors from coming back up through your plumbing.

Also, I agree with Bill that you definitely don’t want to try to replace the gray tank.

[DennisB]

Shane-thanks, I will give it a shot ….
Dennis

[Bill]

I agree with Shane about the p-traps, and that should have been my first answer. My idea of a decomposing critter inside the tank is much less likely. But in the event that it is right, the stink would have stopped when you cleaned out the tanks and cleaned off the carcass, but then would have come back a short time later, when decomp restarted. In that case, the stink would go away permanently when decomp reduced the size of the remains to the point where they could wash out through the drain opening.

It is not unheard of for critters - both 4-legged and no-legged (snakes) to crawl up an open drainpipe, especially if the weather gets a little cold. That is one reason never to leave the valves open.

Bill