Backflow preventers are now required on both residential and commercial buildings. They are designed to prevent any contaminated water source from flowing backward into our residential or commercial drinking water systems. Residents are required to both install a backflow preventer and to have it tested regularly as by a licensed plumber or certified tester according to county requirements.
The easiest way to explain how a backflow preventer works is to think of a one-way valve. Water flows normally from the utility supply pipe under the street into homes and businesses. If for some reason the utility water pressure dropped and there was a source of contamination such as a faulty toilet or other sources, that contaminated water could theoretically flow back into the public utility system and contaminate other homes. That is why each service connection to a home or business water supply must have a backflow preventer. If you don’t have a backflow preventer on your water supply, check with your county to determine if one is required.