The Principle Operation of a Dual Check Valve Backflow Prevention Device – No Water Out of the Box
The DuCV out-of-the-box does not come equipped with shut-off valves and the check valves are in a closed position. The check valves are replaceable are typically constructed of plastic with stainless steel springs, rubber O-rings and should never be directly soldered into the service line. The DuCV is available with thread or solder end connections. The check valves shall be removed if excessive heat will be applied when soldering near the DuCV. The DuCV is not testable and the check valve may become fouled by debris in the service line connection. The service line shall be flushed thoroughly to remove foreign matter from the service line before installation of the DuCV. If there is evidence of debris in the service line that may foul the check vales, a wye strainer shall be installed upstream of the DuCV. The DuCV will have marking indicating the direction of flow. The DuCV come is in several sizes and shapes. There are two types one used for service lines and the other used for residential fire sprinkler systems. The DuCV used for residential fire sprinkler systems comes in 1 inch to 2 inch sizes.