Morning Vanleigh Owners
Need some help with a problem I am having with a 2020 39fbb, every time we move we are getting a Black Tank smell throughout the camper, after setting up and airing it out no more smells, what I have done trying to rectify is to wrap plastic around each Air Admittance Valve one by one trying to isolate it to a valve, but no luck so far, now we are getting that smell when i turn the A/C down at night and have used the half bath commode, not every time but now and again, we do a lot of C.O.E. camping but i always flush the tank out till water comes out clean. Just not sure where to go from here, any suggestions would be greatly appreciated.
Thanks Spud
Morning Spud - We have the same year and model as yours. I’d suggest checking the blank tank vent pipe connections. The vent pipes for both black and gray run from the tanks in the wall between the bedroom and the half bath.
In this thread you can see the plumbing layout and how those vent pipes connect to the tanks and all run together to the roof.
I’m thinking that if any of those vent pipes have a loose connection or are cracked that could account for the smells in the RV. Those gray tank smells can be just as bad if not worse than the black tank 
.
You should be able to access those vent pipes from the storage compartment if you remove that diagonal wall section and can squeeze yourself in there enough to get your hands on the vent pipes. If those vent pipes are easily moved up and down that could allow the joints to open enough to allow the tanks to vent inside the RV. You could also gain access to those vent pipes by removing the wallboard in the half bath (the one with the GFCI outlet on it), but that would be a huge PITA.
Another possible source of the smell would be the gray tanks. If they are able to vent into the RV through the drain lines it could smell just as bad. The P traps for the sinks in the master bath, half bath and kitchen should have some water in them to create barrier. Also the HEPVO valves used for the shower and the washing machine should be checked.
I think those are the things I’d start checking on and hopefully this helps you track down the source and eliminate it.
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Thanks Stuart for the comeback, this is really bothering me, I was able to get into the basement and check on the pipes going in and out of the tanks, all seem tight, plus we do not get a smell in the basement just the living space. Did go and smell around the shower drain and there was certainly a bad odor there, took the front panel off and saw the Hepvo valve but going to need someone a lot smaller than myself to get in there to get it out, will probably just cover that drain up and wait till next travel, checking on line did see a couple of utube video’s where the vent pipe did not go through the roof and the odor was circulating through the ceiling vents, looked at removing panel and think I will be able to remove toilet and pull the panel back enough to get a look inside, but will start with blocking shower drain first
Thank you for your responce
You’re welcome and good luck! I’ll be interested to see if blocking the shower drain turns out to be the source. The actual roof vent is also a good place to check to see if the pipe properly connected and fairly easy to access.
Blocking the shower drain did not work, Neither did wrapping the air admittance valves, so the next step is to check the vent pipe, on the fence right now whether to just remove the cap on the roof and take a look to see if the vent pipe is high enough, or to take out the wall in the half bath, leaning to the wall as that will give me a much wider view of all the connecting pipes. Stuart if you get to read this could you please look into your storage area where we have two 1/2" pipes coming from bath area, one of mine after putting level on it falls backwards, it is the one closest to the door, please check if yours does the same
Many Thanks
Hey Spud - Are you checking those drain pipes under the floor from the storage compartment area or in another location? Mine in that are under the floor seem to be pretty level and secure down pretty well (no movement that I’ve seen).
Checking the roof vent to insure the vent pipe is making it that far is a good idea as well.
I am not sure about your vent stack in your floor plan but this is mine which is likely similar. Vanleigh vents up through one stack so if there are loose connections you may get an idea from the pic.
I would check the connections behind the wall in the storage to make sure they are connected to the tank. There has been several folks that removed their vent cover on the roof to find that the vent stack pipe was cut to short allowing air to drift back into the unit.
Hi Stuart & Ryan really appreciate the feedback and picture very informative, I will get a picture of the pipes I am talking about but I do not think that is my problem, thinking about it I am now leaning to take the vent off and make sure pipe is higher than roof, that will probably be easier than taking the wall out. Will also get back into the area behind storage wall and pull and push those pipes into tanks, but as I said there is no smell in basement just the living space, and only while it was moved, no smell parked, except a couple of times it has smelled through the AC vents. Let you know if I find anything. Thank You