What does a backflow preventer do?

A backflow preventer is a critical device designed to protect potable water supplies from contamination or pollution due to backflow. Backflow can occur when there is a change in pressure in the piping system, which causes the water to flow in the reverse direction. This can lead to unsafe substances entering the clean water supply, posing health risks.

The primary function of the backflow preventer is to ensure that water flows only in one direction, from the water supply into the plumbing system. By doing so, it effectively safeguards drinking water from potential contaminants that may be present in waste systems or other non-potable sources. This protection is essential in maintaining public health standards and ensuring the safety of water that is consumed by individuals.

The other options do not accurately describe the function of a backflow preventer. Measuring water flow, filtering water, or supporting drainage systems are tasks that relate to other types of plumbing devices or systems, but they do not encompass the primary purpose of preventing backflow.