I'll ask how big is too big?
We have a 32g gray and 32g black tank. We know we will come close to filling the gray in 4 days so DW will wash dishes in a container that fits in the sink and I dump it into the black tank. After 4 days we may have a full gray tank but the black is maybe half full at the most. I still have to add water into the black tank to fill it before I empty it.
It's just the two of us using the facilities.
So I'm curious, how many here have to add water to their black tank to get it close to full before draining it?