Not many things are more bothersome than waiting for the water to get hot. This is usually because of the distance from water heater to fixture. Watts makes a thermo sensor / circulating pump assembly to solve this problem. Both Lowes and HD stock it. Selling price is about $200. Installation is a do it yourself project. Basically it's a sensor that connects between hot and cold at fixture. Timer starts pump, and sensor allows cool water from hot to return via cold to water heater. When sensor detects water becoming hot, it closes. Set timer to when you need hot water (morning shower,etc.)