Which device prevents water that may be contaminated from mixing with a public water system?

• A. Deluge Valve
• B. Anti-Siphon Device
• C. Check Valve/Backflow Preventer
• D. Water Flow Indicator/Pressure Flow Preventer

Answer: (C)

Preventing contamination of the public water supply comes down to stopping any reverse flow from a potentially contaminated system back into the potable line. The device that does this is a backflow prevention assembly (often a check valve or dedicated backflow preventer). It lets water flow normally toward the system but closes off if pressure on the downstream side would push water back toward the public supply, stopping backflow due to pressure drops, backsiphonage, or backpressure.

Other options don’t provide the same comprehensive protection. A deluge valve is part of sprinkler control and isn’t designed to block backflow into the public system. An anti-siphon device helps prevent siphoning at a fixture, but it’s not a guaranteed barrier at the service connection for all cross-connections. A water flow indicator or pressure flow preventer monitors or controls flow but does not prevent backflow into the public water supply.