The water heater on our Sunseeker 3100 is under the kitchen sink. The water heater bypass valves are inside the cabinet in front of the water heater, as viewed from inside the coach. You should see three quarter turn valves in the tubing. They look like the shutoff valves on your house's toilets or sinks. The blue tubes are for cold water and the red tubes are for hot water. To bypass the water heater, close the valves that allow cold into and hot out of the water heater and open the bypass valve in the cold water line.
If you like, I can post a photo in a few days. We will be getting ours out of storage for family visitors.