The backflow preventor described for the pedicure chair hazard is of which principle?

The backflow preventor described for the pedicure chair hazard is of which principle?

• A. Reduced pressure principle
• B. Double check valve
• C. Atmospheric vacuum breaker
• D. Pressure relief valve

Answer: (A)

This question is about how backflow preventers stop contaminated water from entering the potable supply, especially in a high-hazard setup like a pedicure chair. The principle at work here is reduced pressure. A reduced-pressure principle backflow preventer uses two check valves with a relief valve between them that vents to drain. If backflow conditions occur—whether from backsiphonage or backpressure—the pressure in the space between the checks drops below the supply pressure, the relief valve opens, and water is discharged to the drain. That creates a protected, reduced-pressure zone and prevents contaminants from being drawn back into the potable water supply. This is crucial for a pedicure chair, where used bath water and chemicals could otherwise contaminate the drinking water supply. Other devices don’t provide that same level of protection in this scenario. A double-check valve has two checks but no relief valve to vent a potential backflow, so it’s not the same reduced-pressure mechanism and is suited for lower-hazard situations. An atmospheric vacuum breaker vents to the atmosphere to prevent backsiphonage but can’t handle backpressure and must be placed above fixtures, so it doesn’t offer the same protection in a circulating pedicure spa. A pressure relief valve is about relieving excess system pressure, not preventing backflow into the drinking supply.

This question is about how backflow preventers stop contaminated water from entering the potable supply, especially in a high-hazard setup like a pedicure chair. The principle at work here is reduced pressure. A reduced-pressure principle backflow preventer uses two check valves with a relief valve between them that vents to drain. If backflow conditions occur—whether from backsiphonage or backpressure—the pressure in the space between the checks drops below the supply pressure, the relief valve opens, and water is discharged to the drain. That creates a protected, reduced-pressure zone and prevents contaminants from being drawn back into the potable water supply. This is crucial for a pedicure chair, where used bath water and chemicals could otherwise contaminate the drinking water supply.

Other devices don’t provide that same level of protection in this scenario. A double-check valve has two checks but no relief valve to vent a potential backflow, so it’s not the same reduced-pressure mechanism and is suited for lower-hazard situations. An atmospheric vacuum breaker vents to the atmosphere to prevent backsiphonage but can’t handle backpressure and must be placed above fixtures, so it doesn’t offer the same protection in a circulating pedicure spa. A pressure relief valve is about relieving excess system pressure, not preventing backflow into the drinking supply.