This standard applies to Double Check Backflow Prevention Assemblies (DC) and Double Check Fire Protection Backflow Prevention Assemblies (DCF). These assemblies consist of two (2) independently acting check valves, internally force loaded to a normally closed position, two (2) properly located, tightly closing shut-off valves, and properly located test cocks. They are designed and constructed to operate under intermittent or continuous pressure conditions. This standard also applies to Manifold Double Check Backflow Prevention Assemblies consisting of two (2) or more complete Double Check Backflow Prevention Assemblies in parallel.