On mine, ST 270BH, the hot water heater just fills when either the city water connection is hooked up or if I'm using the water tank, when the water tank is full and I'm running the water pump. If the valves are in the correct position, your HW tank should just fill -- but as I said, that's on my unit. Not sure if its the same on all. You can try it out, put on the hose, wait a few mins. Turn on your hot water heater and wait about 15 mins. Do you have hot water? If so, then your good.
Toyota Tundra 2014 CM 5.7L
Sunset Trail 2014 ST270BH