The purpose of Double Check Backflow Prevention Assemblies (DC) is to keep polluted water from flowing into a potable water distribution system when some abnormality in the system causes the pressure to be temporarily higher in the polluted part of the system than in the potable water supply piping. These assemblies consist of 2 independently acting check valves, internally force loaded to a normally closed position, 2 properly located tightly closing shut-off valves per Section 1.3.2.6 and properly located test cocks per Section 1.3.2.4. These assemblies are designed and constructed to operate under intermittent or continuous pressure conditions.