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

The purpose of an expansion tank in a plumbing system is to absorb excess pressure caused by thermal expansion of water. When water is heated, it expands, which can lead to increased pressure in the plumbing system. This pressure can potentially damage pipes and fixtures, or trigger pressure relief valves. An expansion tank acts as a buffer that accommodates this additional volume of water when it expands, thereby maintaining a stable pressure within the system and preventing wear and tear on the plumbing infrastructure. This functionality is crucial to ensure the longevity and safe operation of the plumbing system, particularly in systems involving water heaters.

Other options, while related to plumbing, do not pertain to the primary function of an expansion tank. Regulating water flow is handled by valves and other flow control devices, preventing pipe corrosion involves various protective measures or coatings, and filtering impurities is the role of water filtration systems. Each of these functions is essential in plumbing but does not relate specifically to the task of managing thermal expansion.