I agree with your philosophy of filling the holding tanks almost full prior to dumping. However, my wife and I go to all the home Penn State football games and rarely get half-full over two nights. We stop at a campground on our way home and dump every trip. Do we have to do this every trip or can it sit in the tanks 2-3 weeks and then dump after the next run? How long can you go between dumps? Ray T.
As long as you are using a quality, enzyme-based, live bacteria tank additive like Pure Power Blue, I see no problem with leaving the tanks partially filled over the course of a couple weeks. The enzymes will continue to work, further breaking down the solid waste. It’s more of a personal choice rather than a technical mandate. But if you wish to evacuate the tanks sooner, simply fill the tank above the 3/4 mark with fresh water and dump after every trip home. This is probably what I would do, but again, there is no harm (unless odors develop) in having a partially filled holding tank when you start for the next home game.
Some coach owners might argue that they’d rather not travel with that additional weight — especially if they refill the fresh water tank before the start of each trip. As a safety concern, you do not want to have more fresh water on board than you have capacity to capture and retain in the black and gray holding tanks combined. Leaving waste in either tank may push you past your total capacity if you refill the fresh tank before evacuating the waste tanks. It does require some diligence from the user.