Let me correct this one, i thought Tree14 has a 4200 Cyclone. if yes, front bath toilet goes to front black, front bath shower and sink and if equipped, washer go to front gray, rear bath toilet goes to rear black, kitchen sink, rear bath, and rear sink all go to rear gray. Thus if you used your kitchen, you were filling the rear gray.
Did that answer your question? BTW, learned this one a bit the hard way....