Which backflow prevention device is used at the portable meter in this context?

• A. Air gap
• B. Check valve
• C. Double-check valve
• D. Reduced-pressure zone backflow preventer

Answer: (D)

Backflow prevention is about stopping contaminants from being drawn into the potable water line when pressure changes. For a portable meter installation, you need strong protection against both backsiphonage and backpressure because the setup can connect to sources or configurations that raise cross-connection risk.

A reduced-pressure zone backflow preventer provides the highest level of protection. It uses two check valves with a monitored space between them and a relief valve that vents if pressure in that zone drops. If any backflow tendency occurs, the relief valve activates to prevent reverse flow, so contaminants can’t enter the distribution system. It’s designed for higher-hazard situations and is testable by certified personnel, which is why it’s the best fit for portable-meter applications.

An air gap offers physical separation but isn’t always practical or permitted for inline connections in portable-meter scenarios. A single check valve or a double-check valve provides less protection and may not guard against all backsiphonage scenarios, especially under backpressure or high-hazard conditions.