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

An expansion tank serves a crucial role in managing the pressure within a plumbing system, particularly when hot water is heated in a closed system. When water is heated, it expands, leading to increased pressure in the pipes. This can create a situation where excessive pressure might cause damage to the plumbing system, including potential leaks, burst pipes, or failure of fixtures.

The expansion tank is designed to absorb these pressure fluctuations by providing a space for the expanded water to go. It typically contains a bladder or diaphragm that separates the water from an air chamber, allowing it to compress as the water expands. This prevents undue stress on the rest of the plumbing system and helps maintain a safe and stable pressure level.

Other choices do not accurately represent the function of the expansion tank. For example, filtering impurities pertains to water treatment options rather than pressure regulation. Similarly, an expansion tank does not eliminate the need for a water heater; rather, it complements the system by ensuring safe pressure levels. Lastly, while water supply pressure is important, the expansion tank does not serve to increase pressure; instead, it mitigates pressure increases resulting from heat expansion.