Massachusetts 2nd Class Fireman Practice Exam 2025 – Complete Prep Guide

The primary function of an expansion tank in a hot water heating system is to accommodate the expansion of water as it heats up. When water is heated, it expands, which can increase the pressure within the system. Without a means to manage this increased pressure, it could potentially lead to leaks or damage to the system. The expansion tank absorbs this expansion, allowing for a safe and controlled environment within the heating system.

In contrast, options that reference the expansion of hot air or steam do not apply since the function of the expansion tank is specifically related to water. An expansion tank is not used for air or steam, as those are separate systems with different requirements. Furthermore, the assertion that an expansion tank is not used in hot water systems is incorrect, as it plays a critical role in managing water pressure and preventing potential system failure.