Frequently Asked Questions

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.

These are the four most common types of backflow prevention methods/devices: 1. Air Gap Separation (AG) An AG is a physical separation between the supply pipe (or faucet) and the flood level rim of its receptacle. 2. Pressure Vacuum Breaker (PVB) The components of a PVB valve are: two independently acting valves (check valve & air valve); test cocks & 2 shutoff valves. This valve is commonly used for irrigation systems. 3. Double Check (DC) Valve The components of a DC valve are: 2 single check valves, test cocks & 2 shut-off valves. This valve is commonly used to protect against low to medium hazard installations such as firefighting systems which does not use toxic additives. 4. Reduce Pressure (RP) Valve The components of a RP valve are: 2 single check valves, 1 relief valve, test cocks & 2 shut-off valves. This valve is commonly used to protect against high hazard installations such irrigation systems that use chemical additives; or firefighting systems that use toxic additives (antifreeze).