[Bob86ZZ4]

I used to have a 32' Allegro class A gas rv. It had 66 gallons of fresh water, 32 gallon gray, and 32 gallon black. The gray tank would almost always fill before the black. My current truck has 200 fresh, 75 gallon gray, and 25 gallon black. You can see now I need to flush out the gray and black twice with each fresh fill. It works well since it's often easier to find a dump than a fill station. The ratio seems to be pretty good too. I was at first worried I'd be filling the black well before the gray. But it doesn't seem to work that way. They both seem to fill about the same time, or pretty close anyhow. As for combining gray and black into one tank. I don't think I'd do that if you can avoid it. The main reason being it's sure nice to rinse that hose with the gray water after dumping the black tank. You'd be dealing with a biological mess trying to rinse out the hose after dumping from a combined tank, wouldn't you? When I'm dumping the gray tank I grab the hose and wriggle it around a bunch to rinse it out better. I don't know, maybe it doesn't help any but it makes me feel better.