What is the principal function of an expansion tank in a hot water system?

The principal function of an expansion tank in a hot water system is to maintain working pressure. As water is heated, it expands, which can lead to an increase in pressure within the system. An expansion tank is designed to absorb this excess pressure, allowing for safe expansion of the water while preventing potential damage or failure of the system due to overpressure. By providing a designated space for the expanded water, the expansion tank helps maintain a consistent and safe operating pressure throughout the heating system, ensuring that components like pipes, valves, and the water heater itself are not subjected to stress beyond their design limits. This function is crucial for the longevity and safety of the hot water system.