What role does a double-check valve assembly play in backflow prevention?

A double-check valve assembly is essential in backflow prevention because it provides double protection against the reverse flow of water in a plumbing system. This assembly consists of two independent check valves that allow water to flow in one direction while preventing any backflow. Should one valve fail, the second serves as a fail-safe, ensuring that contaminated water does not enter the potable water supply. This dual mechanism effectively reduces the risk of back-siphonage or back-pressure, which can lead to the contamination of drinking water.

The other options highlight functionalities that are not associated with a double-check valve assembly. Regulating water pressure is typically handled by pressure regulators, while measuring water purity involves testing equipment and not valves. Similarly, a double-check valve does not serve as a storage unit; instead, it works as a protective barrier in the water delivery system.