Q: It appears I have three tanks, a black and two grey tanks? What goes into each one?
A: Normally 3 tanks, a black tank, and 2 grey tanks(with one known as galley tank), that being said, black is toilet and two grey tanks are for kitchen sink, bathroom sink, bathroom shower/tub, dishwasher and washing machine(last two you might not have), then it is split with one being kitchen sink(galley tank) and the bathroom sink/bathtub/shower). At least all of the RVs I am seeing on a daily basis, those are the common setups.