StirCrazy wrote:
what button are you talking about? I am not sure even if i have this button how it would back flow up hill.
Without being there to point, I don't know how to tell you other than the button is in the middle of the backflow preventer. As far as water flowing uphill, I doubt that the shore water inlet is higher than the showerhead. Open the showerhead valve to vent the pipes, and water will backflow. My kitchen faucet is higher than my shore water inlet, so I can open my kitchen faucet for that.
(That is also how I get RV antifreeze into that section of piping.)