Backflow Prevention Assemblies Questions with well explained answers

Cross Connection - Answer-Is simply a point on a water system where a polluting substance may come in contact with potable water. Backflow are required in - Answer-Every cross connection has a potential to pollute the potable water supply What are the two forms of backflow - Answer-- back pressure - back siphonage Back Pressure (Irrigation side) - Answer-This type of backflow occurs when the pressure from the irrigation system is greater than the pressure from the water supply. What causes back pressure - Answer-A pump installed downstream the water supply, gravity, and water hammer Back Siphonage (City SIde) - Answer-This type of backflow occurs when the pressure from the supply side drops and draws the water from the irrigation system into the water supply. What causes back siphonage - Answer-A break in the city water main, also when the fire department pumps large quantities of water through the city's water main. Air Gap - Answer-is a physical break that seperates the polluted water from potable water. Examples of Air gaps - Answer-A common example is the sink. Dirty water in the sink can not go into the faucet Requirements for an Air Gap - Answer-- The gap must be an unobstructed, physical separation - The gap should be two times the diameter of the supply piping, but never less than 1" - It is approved for potential health hazard conditionsIt is an approved method of backflow prevention when chemicals are added to the system. Pressure Vacuum Breaker (PVB) - Answer-Prevents back siphonage. Has a spring-loaded check valve which closes when the flow of water stops. Also has a spring-loaded air inlet valve which opens to break the siphon water the pressure drops to 1 psi. Requirements for a Pressure Vacuum Breaker (PVB) - Answer-- It protects against back siphonage only - It can be under constant pressure (more than 12 hrs) - It must be installed at least 12" above the highest downstream piping and/or opening - It is approved for potential health hazard conditions - Must be tested by a licensed backflow prevention assembly tester upon installation and annually if health hazard conditions exist - 2 test cocks - 2 shutoffs Double Check Valve Backflow Prevention Assembly (DCVA) - Answer-They can be installed below grade where local codes allow. It should have enough clearance underneath for easy access, and to reduce the rist of being submerged in water. It can be installed in a horizontal or vertical position. It has two spring loaded check assemblies with captured springs and silicone seat discs. Internal parts should be repaced without special tools. Double Check Valve Backflow Prevention Assembly (DCVA) Requirements - Answer-- It protects against back siphonage and back pressure - It can be under constant pressure - It is approved for non-health hazard conditions but NOT APPROVED for health hazard conditions - Must be tested upon installation by a licensed backflow prevention assembly tester. - 4 test cocks - 2 shutoffs