What is the function of an expansion tank in plumbing?

The function of an expansion tank in plumbing is to absorb excess pressure in a closed water system. When water is heated, it expands, and this increase in volume creates pressure within the plumbing system. An expansion tank provides a space for this expanded water to go, which helps to prevent excessive pressure from damaging pipes and fixtures.

By incorporating an expansion tank, the plumbing system can accommodate the fluctuations in pressure that occur due to temperature changes. This is particularly important in systems that use water heaters, where heating water can significantly increase pressure levels. The tank effectively maintains a stable pressure, ensuring the system operates safely and efficiently.

Options that suggest boosting water pressure, filtering impurities, or cooling hot water do not accurately describe the specific role of an expansion tank, which is solely focused on managing pressure changes within the system.