Definitions

• Air Gap - means a physical separation, between the discharge end of a supply pipe and the top rim of its receiving vessel, of at least one inch or twice the diameter of the supply pipe, whichever is greater.
• Backflow - means a reverse flow condition that causes water or mixtures of water and other liquids, gases, or substances to flow back into the distribution system. Backflow can be created by a difference in water pressure (backpressure), a vacuum or partial vacuum (backsiphonage), or a combination of both.
• Back Pressure - The difference between the pressure within any water service and a higher pressure within any vessel or pipework to which it is connected.
• Backflow Prevention - minimizing the risks of contaminating the potable water supply. Usually referred in context as a backflow prevention program.
• Backflow Prevention Assembly - A device to prevent backflow. There are a number of different devices including a reduced pressure device, air gap and a double check valve.
• Backsiphonage - condition that occurs when the water supply pressure falls below atmospheric pressure and causes backflow.
• Contaminant - Any solid, liquid or gas with potential to enter or pollute the potable water supply.
• Cross Connection - A physical connection between the potable water system and any other source of water or other substance which under certain conditions, may lead to contamination of the drinking water supply through backflow.
• Distribution System - all physical components of the water supply system, including water pipes, reservoirs, booster pumps, hydrants and other means used to deliver drinking water to the customers.
• Double Check Valve Assembly - a backflow-prevention assembly that contains two independently acting check valves with tightly closing, resilient-seated shut-off valves on each end of the assembly and properly located, resilient-seated test cocks.
• Pressure Vacuum Breaker Assembly - backsiphonage prevention assembly that contains an independently operated, internally loaded check valve; an internally operated air-inlet valve located on the discharge side of the check valve; tightly closing resilient seated shut-off valves on each end of the check valve assembly; and properly located resilient seated test cocks.
• Potable System - all components of the water system from the source of the potable water through the distribution system.
• Reduced Pressure Principle Assembly - a backflow-prevention assembly that contains two independently acting check valves; a hydraulically operating, mechanically independent pressure differential relief valve located between the two check valves; tightly closing, resilient seated shut-off valves on each end of the check valve assembly; and properly located resilient seated test cocks.
• Water Hammer - A pressure surge caused by a rapid change in pressure or flow. The noise (bang) is the collapse of vapor bubbles in areas of low pressure. The resultant pressure surges can damage plumbing systems.