I am not sure I really understand the issue. In any case I have a system that has worked well for me. I bought a simple timer at the dollar store. I set it for the time needed to heat the water to shower temperature. With my 6 gallon Atwood that is about 15-25 minutes depending on the initial water temperature. When I take a shower I only turn on the hot water and the temperature is consistent for the typical shower. I like hotter water so I usually take the first shower. By then the water has cooled to the point that my wife likes.