In New York City, your drinking water is pushed from the city’s main lines into your property through pressure, and it should only flow in one direction. However, pressure changes in pipes can sometimes cause water to flow backward, potentially contaminating the public water supply with harmful substances or chemicals. New York State law mandates that certain properties and businesses install, maintain, and test backflow prevention devices to prevent such contamination. Failure to comply with these regulations can result in fines or water service disconnection.