2017 Newmar Baystar

I think you will find that hose only lets you pump RV antifreeze into the water lines. Usually, to sanitize the fresh water tank you need to pour bleach into the fresh water fill inlet. I haven't seen any RVs where the pump is able to put water into the fresh water tank. The valve associated with that hose most likely only allows selecting the hose OR the tank as the liquid supply to the pump. Isn't that second valve just a drain (to the ground) for the plumbing in the wet bay? To winterize, you first have to change the water heater lines to "bypass" so you can pull the heater plug and drain it. Without that bypass, you would have to fill the entire water heater before the lines got winterized, requiring gallons of antifreeze. Don't forget the icemaker line!