When you say the word "backflow" most people think about a drain backing up. In the plumbing world, however, “backflow” refers to the water distribution side of things. A backflow preventer such as a check valve, or an RPZ (reduced pressure zone valve) are devices that are installed in your piping system to prevent bad water from backflowing into your goo drinking water. On a low hazard situation a check valve may be all that is required, but when you are talking about the supply to a boiler that has chemicals in it or a lawn sprinkler system you need the greater protection that is provided by an RPZ. The RPZ has 3 components that are designed to give very good protection. It has 2 internal check valves and a third component, a relief that will open and dump the bad water in the event that either of the 2 check valves fail. In the highest of hazard situations where you need 100% guaranteed the protection of the drinking water system, we install what is called a cut off system. A cut off system actually has a complete separation of the danger from the drinking water. It fills a tank with an atmospheric break so that there is no physical connection. Once the water is delivered to the tank it is then repressurized and delivered to the area of concern. All of the plumbers at John Baethke are specially licensed to identify backflow dangers and how to address them. We all have what is called a CCCDI License. That stands for Cross Connection Control Device Inspectors License.