What are Backflow Preventers?
Backflow preventers, also known as Reduce Pressure (RP) or Double Check (DC) devices, or Pressure Vacuum Breaker (PVB) devices, protect the city's water supply from outside contamination. The devices operate by allowing water to flow in only one direction. In an unprotected water service connection, potable water can, and does, flow both in and out of a building or fixture. When water service is interrupted in the street or in a building for any reason, there is a pressure drop which can draw contaminated water backwards into the water system. For example, cleaning fluids may be drawn back from car washes; stagnant water from fire sprinkler systems may enter the drinking waterline; bacteria and pathogens of all sorts can be siphoned back into the water system from air conditioning cooling towers; and chemicals from medical clinic's xray development may flow backwards into the potable water system. To protect water quality, backflow protection is required where the end user poses a risk of polluting the city's water.

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1. What are Backflow Preventers?
2. Types of Backflow Devices
3. How to winterize your irrigation backflow device