Don't turn the electric heat element on unless you're absolutely sure it has water in it. The bypass valves are easy to figure out if you just study them a little. When the handle is inline with the pipe, it's open. Make sure the valves are set so water flows into and out of the tank.
03 Chevrolet Silverado 1500, 5.3 V8, 3.73
06 Rockwood Roo 23SS