As I am taking a shower, the water temp is changing in relation to the water pressure. As the pressure reaches cut out pressure at the tank the temp is hotter, and cools as the pressure drops to the start pressure. I have a new water heater and the pressure switch is set at 35-65 psi and is working correctly. Any ideas how to stop this? The temp difference is about 10-15 degrees from high to low. Thanks for any ideas.