How Does a Thermal Expansion Tank Work?
Most new systems today have a backflow preventer, a water meter with a check valve, or a check valve in the system which creates a closed loop system. When water in your water heater heats up, it expands with no place to go except through the pressure relief valve. A thermal expansion tank is installed on the cold water side to provide a reservoir for the expanded water. The water can safely be stored in the tank until its released on demand.