Black Tank capacity

[BendOrLarry]

I bet it's a vent issue. Either at the top on the roof or paper blocking it inside the tank. If the toilet flapper seal is good (holds water above it when closed) then it just about has to be a venting problem.

[5picker]

How long does it take to get to 25 gallons or the point where it starts to stink?

You did mention this was your first seasonal site. If you are leaving the black tank set between visits without dumping and it takes a month or more to get to the 25 gallon mark, I'm not sure anything you put in there will stop the smell.

Portable holding tanks are designed to be used and emptied on a pretty regular basis whether full or not. Holding tank chemicals are not designed to work for months. If you leave the stuff in there for any length of time, it's going to smell.

[CC75]

jackssilverback29, did you ever get this resolved? If so how?

[lupie989]

I have found the most effective odor control treatment consist of ...two cups bleach, cheap dish washing detergent (cup) and water softener. (cup) Add to tank after flush, along with gallon of water. I have not noticed any odor since using this mixture.