As a point of reference, on our 24 foot Class C the gray tank is 29 gallons and our black tank is 39 gallons.
Our kitchen sink and shower drain into the grey tank. Our bathroom sink and toilet drain into the black tank.
Via valves, the two tanks can be temporarily combined for a total grey-black capacity of 69 gallons ... just in case one tank should fill way ahead of the other.
I wonder how many folks pay attention to tank capacities as criteria when shopping for a new or used RV? IMHO, tank capacities is a very important consideration.
