Which of the following is the primary function of a backflow preventer?

The primary function of a backflow preventer is to prevent contamination of potable water. This device ensures that water flows in one direction and effectively blocks any reverse flow that could occur from various causes, such as a drop in water pressure in the distribution system. By stopping the backflow of water, backflow preventers protect drinking water supplies from pollutants, chemicals, or waste that might be present in the water supply that could otherwise enter the clean, potable water system.

Improving water pressure refers to enhancing the force or volume of water being delivered, which is not a function of a backflow preventer. Allowing reverse flow of water contradicts the primary purpose of the device, as its role is to maintain a unidirectional flow to safeguard clean water. Monitoring water usage entails measuring the amount of water consumed, which is typically the function of flow meters, not backflow preventers. Therefore, the correct answer accurately highlights the essential protective role that backflow preventers play in ensuring safe drinking water.