The expansion tank's primary function revolves around compensating for changes in______?

The primary function of an expansion tank is to compensate for changes in water volume within a closed hydronic heating system or a hot water system. As water is heated, it expands, which can increase the pressure within the system. The expansion tank provides a space for this excess water volume to flow into, thereby maintaining system pressure and preventing potential damage or leaks due to overpressure.

While temperature changes do influence water volume through thermal expansion, the direct relationship that the expansion tank addresses is specifically about the volume of water caused by such changes in temperature. Therefore, it is critical in regulating the water volume in conjunction with temperature fluctuations, ensuring the system operates efficiently and safely.