What is the primary function of a check valve in plumbing systems?

A check valve is specifically designed to prevent reverse flow in plumbing systems, ensuring that water moves in only one direction. This is crucial in maintaining the integrity of a plumbing system, as allowing water to flow backward can lead to contamination of clean water supplies, damage to appliances, and system inefficiency.

In various applications, check valves are particularly important in systems that involve pumps, as they help prevent backflow when the pump is not operating. By blocking the reverse movement of water, they help maintain pressure and ensure consistent water supply to fixtures and appliances.

The other options do not represent the primary function of a check valve. Measuring water pressure involves devices like pressure gauges, regulating temperature is accomplished by thermostatic valves, and filtering impurities is done by filters or strainers, not check valves. Thus, the key role of a check valve in plumbing is effectively to prevent reverse water flow.