On my present and past Keystone products, one a TT, new one a fifth wheel, BOTH switches were "flush" on the rear of the hot water heater tank, accessed by removing a panel in the cargo area ( 2 screws ). The "switch" is like the end of a toggle switch and is flush mounted right on the tank at the point of entry of water from the feeder line to the tank. It can be difficult to recognize as it is neutral color, same as all the white and clear tubing back there. Hunt and run your hands up on the back and you will see it and feel it. Simply rotate it and presto, you are either in or out of adding city water at your preference.