Lack of Hot water

It's a simple fact that no matter how you heat the water, 6 gallons is not going to afford anybody a long hot one. We, too, have only a 6 gallon water heater, and have had no issues doing two or even three showers after washing the dishes. The trick is what's called a Navy shower: get the water going, wet yourself down, and shut off the water. Soap up, and rinse off.

You, however, may find satisfaction by replacement of the 6 gallon WH tank with an on-demand water heater. They do make them for RVs.