Gas Fitter Practice Test 2025 - Free Gas Fitter Practice Questions and Study Guide

The primary function of expansion tanks in a water system is to accommodate the pressure fluctuations that occur as water heats up and expands. When water is heated, it expands, which can increase the pressure within a closed water heating system. Expansion tanks provide a designated space for this extra volume of water, thus preventing excessive pressure that could lead to potential failures or damage to the system.

An expansion tank is typically designed to operate under a certain pressure and has a bladder or diaphragm that separates the water from an air pocket. This setup allows the tank to absorb excess pressure and provide a cushion during fluctuations, ensuring the system operates efficiently and safely.

In contrast, the other options address different functions or misinterpret the role of an expansion tank. For instance, cooling water or trapping steam are not related to the primary purpose of an expansion tank. Similarly, while condensate collection is important in steam systems, it is not relevant to the operation of an expansion tank in a water system. Thus, the correct option clearly illustrates the expansion tank's essential role in managing pressure changes within the system.