Sewer smell

[dutchev]

We are noticing a smell of sewer intermittently. we have thoroughly cleaned the black tank, including dumping 3 five gallon pails of water down the toilet. we also used 2 deodorizers.
Help please

[Godzilla2020]

We have 2 Toilets/ 2 black tanks.

The Toilets in the half bath has a seal issue we discovered after noticing a strong urine smell.  So like other have said/ asked  - is it holding water?  For now ours will seal if we lift up on the flush petal after pressing it.

[stripit]

Scott G has it more than likely, those valves can really cause a stink. They unscrew easily and are not expensive.

[Lantley]

Check your plumbing vents on the roof. If the cap is missing you can get a back draft which causes an intermittent smell.

[slider45]

We may deal with the plumbing vents issue. Hope it is just the missing cap

[ScottG]

Grey can smell as bad as black. If your Air admittance valve is under the sink and has failed, that can easily be the culprit. Try covering it with a plastic bag and seal it to the pipe with a rubber band or tape. If the smell stops, you have your answer (dont leave it that way).
The parts they use in RV's are pure junk - one of mine failed the first season. You can get a quality replacement at Lowes or Home depot.

[wildtoad]

Is your bathroom vent open and is it near the black or grey roof vent pipe?

On my mh black vent pipe is less than a foot away from the bathroom vent and when the wind blows in the right direction, or air is sucked into the vent we get a sewer smell.

[enblethen]

Could it be grey water smell? Bad air admittance valve under lav sink.
Make and model of rig?
Anything else dumps into black tank?

[opnspaces]

Are you smelling the deodorizers or just the black tank type of smell? Is the toilet bowl holding water?

If the bowl is holding water it could be a gray tank odor. Are all the P traps full? Do you have an unused washer dryer hookup that might have a dry trap?

If you never smelled the deodorizer try dumping a quart of Pine Sol down the kitchen sink drain. and rinse it well. Then come back in an hour or so and see if yo smell the Pine Sol in the trailer.