What is the role of an expansion tank in a heating system?

An expansion tank plays a critical role in maintaining system pressure within a heating system. When water is heated, it expands. This expansion increases the pressure within the system, which could potentially lead to issues such as leaks or even ruptures in the system if the pressure becomes too high. The expansion tank serves as a buffer that absorbs this excess pressure, allowing the expanded water to flow into the tank rather than increasing the overall pressure in the pipe system. By doing so, it helps ensure the system operates safely and efficiently, protecting both the equipment and the integrity of the heating system.

The other options do not accurately describe the primary function of an expansion tank. While the tank may retain water and manage some volume aspects, its main purpose is focused on pressure regulation rather than simply increasing water volume. It does not have a significant impact on heating time or temperature control, as these functions are managed by the heating source and system design. Thus, maintaining system pressure when water is heated is the central reason for the existence of an expansion tank in a heating system.