What is the primary function of a double check valve?

The primary function of a double check valve is to prevent water from flowing backward, which is crucial in maintaining the integrity of a water supply system. This type of valve is specifically designed to stop the reverse flow of water that could contaminate the clean water supply. When water moves in the intended direction, the check valve allows it to pass through; however, if there is a drop in pressure or a potential backflow situation, the double check valve closes. By effectively blocking the reverse flow, it helps to protect the public water system from pollutants and ensures a reliable and safe supply of potable water.

The other choices pertain to functions that are not relevant to a double check valve; enhancing water circulation and regulating temperature are not the roles of this valve, and increasing fluid pressure is handled by different types of equipment designed for pressure manipulation rather than controlling flow direction.