1. Air Gap Separation - A physical break between the supply pipe and flood rim of a receiving vessel. The separation shall be at least twice the supply pipe size and no less than one inch.
2. Aspirator Effect - Backsiphonage often resulting from a reduction in pipe size or a restriction in the volume of flow.
3. Atmospheric Pressure - The weight of the atmosphere on the surface of the earth. The atmospheric pressure at sea level is 14.7 psia.
4. Atmospheric Vacuum Breaker - A non-testable backflow preventer recognized for protecting against health hazards on specific pieces of equipment or water uses. Consists of an air inlet valve designed only for non-continuous use and back-siphonage conditions.
5. Backflow - The undesirable reversal of water flow in a distribution or supply line. Besides involving polluted or contaminated water, backflow may also occur involving gases or vapors from another substance or source connected to a potable water line.
6. Backpressure - A hydraulic condition in a water line resulting when downstream pressure becomes greater than the incoming pressure. Examples that can cause backpressure are a pump kicking on, elevated piping or thermal expansion.
7. Backsiphonage - A sub-atmospheric condition that occurs in a water line resulting in the reversal of flow.
8. Barometric Loop - The theory of preventing back-siphonage based on the principle that the highest water can be siphoned up into a water line at sea level is 33.9 feet.
9. Double Check Valve Assembly - A testable backflow preventer designed for protecting against low or pollutional hazards only. Consists of two independent check valves, two shut off valves and four test cocks.
10. Flood Level Rim - The top edge of a plumbing fixture or receptacle over which water would flow if it were full.
11. Pressure Vacuum Breaker Assembly - A testable backflow preventer designed for protecting against high or contamination hazards. Consists of an air inlet valve, check valve, two shut off valves and two test cocks.
12. Recycle Water - Water originating from a waste water treatment plant that has been filtered and treated to meet a quality standard acceptable for an intended use. Common uses include landscape irrigation and cooling tower makeup water.
13. Readily Accessible - Referring to a backflow preventer's location, safely accessible for testing and repair. The distance from the ground / floor to the bottom of the assembly shall be no more than five feet.
14. Reduced Pressure Principle Assembly - Testable backflow preventer designed for protecting against high or contamination hazards. Consists of two independent check valves, a pressure relief valve, two shut off valves and four test cocks.
15. Spill Resistant Vacuum Breaker Assembly - Testable backflow preventer designed for protecting against high or contamination hazards. Consists of an air inlet valve, a check valve, two shut off valves, one test cock and a vent valve.
16. Water Purveyor - The agency that's responsible for providing quality water that meets standards set by state and/or local regulations through the Safe Drinking Water Act.