What is the primary function of a backflow preventer?

The primary function of a backflow preventer is to prevent contaminated water from reversing into the main supply. Backflow can occur due to a change in pressure in the water system, which could allow water that is not safe or is contaminated to flow back into the clean water supply. This is crucial for maintaining the safety and quality of drinking water, as it helps to protect public health by ensuring that only clean, potable water is delivered through the plumbing system. The installation of backflow preventers is often mandated by plumbing codes in order to safeguard against potential health hazards caused by backflow contamination.