Plumbing tips: what does anti-siphon or backflow prevention mean?
Whether you own a home or business with outdoor plumbing, chances are good that you’ve heard the terms “anti-siphon” or “back-flow prevention.” These terms, though technically different, generally both refer to the blocking of a fluid’s backward motion through a pipe, particularly one with an open outlet, such as a spigot or lawn irrigation system. To better understand how these devices work, consider this example. When you open a spigot, water flows outward because pressure inside the pipe is positive, meaning that the water pressure exceeds atmospheric pressure. However, when the spigot is closed, the pressure inside the pipe becomes negative, or less than atmospheric pressure. The result is a force known as “siphon,” which causes the backward flow of water through the pipe, a movement known as back-flow. So, anti-siphon refers to a mechanism that blocks the action of siphoning, and back-flow prevention refers to a mechanism that prevents backward flow. The difference between these t
