[Cheif 2]

Use to have a similar problem a couple of years ago until we found out that the pipe they installed from the commode directly into the black tank was to short and after the top of the black tank became slightly concave, which they say is normal, the pipe pulled away from the crappy job of sealing they did causing leakage. I would check the pipe where it enters the black tank. On our model you can see it from the lower compartment, but on yours you may have to remove the toilet and floor flange to get to it. Once the correct length pipe was installed no more odors. Until you can get it fixed make sure you keep you black tank level low. Trust me on that one. That is how we found our problem, if you know what I mean. Good luck!