Noticed the cold water in the bathroom was lukewarm and checked things out. The water heater is in the basement below. Hot water line out of the heater is hot with no fixtures turned on and it is normally cool a short distance from the tank. The cold water line is slightly warm. I checked piping and valves in the bathroom and the shower temperature valve is slightly warm. It seems the valve is leaking between hot and cold and a thermosyphon loop is happening. The temp valve just controls temp and there is a on/off valve after the temp valve. I need to identify the brand/model of valve but I am guessing a cartridge or some internals of the valve need to be replaced. Some of the valves and other parts are Jaclo so that may be the brand of the temp valve. Looking for some advice on what I need to do/what needs to be replaced.