Re: i still can't find the vents for the holding tank
You are absolutely right. Also, iff you want the acid to sit in the hose for a while, you can do the following. While you are pumping the acid into the hose through the toilet you can have a person just running water in through the pumpout opening so that any acid will only make momentary contact with the fitting. Then after you are done pumping and while the acid is sitting in the hose you can fill the tank with at least a few gallons fresh water that any acid that splashed out or continues to leak outd is diluted. Then rinse the tank again once you finally pump the acid out of the hose.
I've posted this before but will mention it again. For those of us that don't plumb our toilets with fresh water--just place an 8" kitchen bowl in the sink. Use the kind that has the soft urethane bottom. After you wash your hands pour the contents of the bowl into the toilet and pump it. Fresh water with liquid soap will sit in the hose. Do the same with toothbrushing or shaving residual--I am convinced that that stuff causes just as much sump smell as food residuals and its mostly fresh water. For the record we dispose of a lot of pots and pans soapy water with food residual through the head as well--if underway, etc.
Bob and Suzanne KAIMI