Hey y'all - we have a 2013 Crusader 335BHS (most awesome coach!), it has 2 gray tanks @ 35g each but plumbed separately. Since we typically camp in state parks w/ electric only, I added one of these: linky
I leave both gray tanks valves open which lets them equalize giving us 70g (plus whatever's in the pipes) capacity. On our 335BHS, the gray tank is for the shower and bathroom sink, the galley gray is for the kitchen & outdoor kitchen sink - we don't use the shower with electric-only hookups, so the galley gray would fill up much faster than the gray tank. By adding the extra waste valve we have a full 70g capacity, extending the time we can go without dumping or needing a tote.
Rig: 2011 F350 CC SB FX4 diesel, aka The Tow Beast
Summer House: 2013 Prime Time Crusader 335BHS