The Rheem Water Heater Booster improves the overall performance and capacity of gas or electric tank water heaters. The booster unit attaches to any tank or nearby wall. Compatible with Electric or Gas Tank The Rheem Water Heater Booster installs directly on the water line to provide more hot water than the tank alone can provide. The booster delivers nearly double the shower time. The unit senses the temperature of the water from the tank outlet, and activates when it senses that its inlet temperature has dropped below the user set activation temperature.