This brings up another question. My Black & gray tanks are also 30 & 40 and my fresh water tank is 46 gallons. Is this 40 plus the 6 gallon hot water tank? The sensor lights on the gray tank say that the gray is full long before the FW tank is half empty, so I found early on that they are not very accurate.
I thought about filling the FW and draining it into the gray to see if it would all fit but not sure what would happen if it doesn't. It seems that it would just start to fill the bathtub from the drain, is that correct?