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

The primary purpose of an expansion tank in a plumbing system is to accommodate thermal expansion of water. When water is heated, it expands, which can increase pressure within the plumbing system. This increase in pressure can lead to potential damage or failure of pipes, fittings, and appliances. The expansion tank provides a designated space for this expanded water to go, allowing the system to manage pressure fluctuations safely.

By absorbing the extra volume of water created by thermal expansion, the expansion tank helps to maintain stable pressure levels throughout the plumbing system, preventing issues such as pipe bursts or leaks that can occur when pressure gets too high. This function is crucial, especially in systems with water heaters that heat water to high temperatures, creating significant expansion.

While the other options mention functions related to storing water, increasing pressure, or preventing leaks, these do not accurately reflect the primary role of the expansion tank within the system. The expansion tank specifically addresses the dynamics of thermal expansion, making it an essential component in ensuring a safe and efficient plumbing system.