In plumbing, what is the purpose of a backflow preventer?

A backflow preventer plays a crucial role in maintaining the integrity of a potable water supply by ensuring that contaminated water does not flow back into it. This device prevents reverse flow, which can occur due to changes in pressure within the plumbing system, such as during water main breaks or when hydrants are opened for firefighting. Without a backflow preventer, there is a risk that harmful substances and pollutants from non-potable sources could enter and contaminate drinking water, which can lead to serious health risks. Ensuring the safe delivery of clean water is a primary responsibility of plumbing systems, and backflow preventers are vital to achieving that goal.