I petitioned FR/Dynamax for documents and they sent me several. Including the tank layouts and drain feeds. The washing machine and front sink actually drain into the the front black tank. The only thing draining into the front grey tank is the galley. The shower and 1/2 bath sink drain into the second grey tank. Based on my recent experience, I have to say they're accurate for our rig.
I received the 3715/37FB 12v, 120v and drain layouts. As well as the 37BH 12 and 120v layouts.
PM me if you would like me to send copies to you or anyone with a 3715FB, 37FB, or 37BH.
2017 CC38EL Silverado 3500HD