What size waste tank to buy?

We bought the 36 gallon unit. VERY heavy when full, but it came with a bracket to drop on a ball hitch, so you only have to lift it about 18" to set it on a ball.
Of course, you don't HAVE to fill it either, so the extra capacity is nice if ever needed.
We have a 53 gallon back tank so it is possible to have more coming out of the tank than the tote can hold. I dread if that should ever happen.

Thank you. We don’t really need to dump waste, but usually the grey tank fills up and can dump that n refill water tank. I’m going to,order the 21 gallon Rhino

do you really need one? Our trailer has a 32 gallon black, and two 32 gallon grey tanks.

DW and I can camp for two weeks without needing to dump. do need to fill the fresh water but not dump.

Even with our daughter, SIL and 2 teenagers we can go 5 days or more without needing to dump.

even a 15 gallon waste tank is going to weight over 120lbs full. 36 gallon pushing 300lbs. Waste tank is going to weight around 8+lbs/gallon

How often do you want to dump? The bigger, the heavier.