What is the primary function of an expansion tank in a plumbing system?

The primary function of an expansion tank in a plumbing system is to absorb excess pressure from thermal expansion. When water heats up in a closed system, such as in a hot water heater, it expands. This increase in volume can cause a rise in pressure within the pipes, potentially leading to leaks or even bursts if not properly managed. An expansion tank provides a space for this expanded water to go, effectively alleviating the pressure buildup. It typically contains a bladder or diaphragm that flexes to accommodate the expanded water, thereby maintaining safe pressure levels in the plumbing system. This function is crucial in ensuring the integrity and longevity of both the plumbing fixtures and the pipes.

The other options do not accurately describe the function of an expansion tank. While increasing water pressure, filtering contaminants, and preventing corrosion are important aspects of plumbing systems, they are not roles played by an expansion tank.