https://www.mchenryplumbing.ca The water in your home is received from a main water supply line, flowing inward so that water enters safely and uncontaminated. However, there are instances in which water can flow backwards due to a change in pressure, going back into municipal water lines and contaminating the water. A backflow preventer can prevent the water from flowing backwards, helping to prevent contaminants from entering the water supply source. https://irp.cdn-website.com/45e12774/dms3rep/multi/McHenry+Plumbing+Welcome+Blog.jpg https://www.mchenryplumbing.ca