I use the SmartTote 2 to empty my tanks when on extended stays. It has 4 wheels and 18 gallon capacity. I can either pull it by hand or hook the handle onto the ball on the rear of the Jeep to transport it to the dump.
It says it has auto shut off but that doesn't account for what remains in the hose, so I watch the float. As soon as it moves I shut off the valve and so far no spills. It is a little bulky but fits nicely on its side in one off the bays. You can even strap it to your ladder on the rear of you RV.
I suggest doing your gray water first to make sure you have the hang of it before attempting the black water for the first time.
I know this wasn't your question, but this solves the concern of filling the tanks and I hated telling everyone to NOT use the toilet. Now I don't worry about it. Less stress and I love it. It gets a lot of use at our annual family reunion campout...6 families mostly with trailers and electric sites only.
Life is good!
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