[Timothy]

Unfortunatley its the norm for just about all products. You could have your sink replumbed to the gray tank or put a swing check valve in the drain line to your sink, that should stop any backup concerns. The trap should keep any odors from coming into the rig a gray tank often smells just as bad or worse then the black tank lol. Contact John Smith at GS and see if they will replumb the tank for you citing your concerns. John had always been very helpful to me. Keep us posted and good luck.