We have a plastic tub that fits very nice in our kitchen sink. We, very seldom let anything go down the drain. We usually do our cooking and cleaning outside, since the camper has the outside camp kitchen. Outside, we'll spray the dishes for a rinse. If washing inside, we catch in the tub. And yes, it is pretty amazing how much water runs over those dishes to rinse them. The tub (inside) usually fills up. I know it's a good couple gallons. We usually dump it down the toilet.
My tanks are 30 gallon on my Keystone. Grey galley is 30, grey shower is 30, and black is 30. And yes, we dump ever 2 days, all 3 tanks. It's just the 2 of us too, and the doggie!
