What backflow prevention device is, at a minimum, required at the portable meter for domestic water booster pumps?

• A. Air gap
• B. Reduced pressure principle backflow preventer
• C. Double check valve
• D. Pressure vacuum breaker

Answer: (C)

Backflow prevention for a portable meter serving a domestic booster pump focuses on preventing any reverse flow into the public water supply when pressure changes occur. The minimum device that provides reliable protection in this setup is a double check valve. It installs two independent check valves in series, so if one valve weakens, the other still blocks backflow. The small vent between the checks helps relieve pressure differences and prevents back-siphonage without allowing contaminants to pass back into the system. This arrangement is suitable for low-to-moderate hazard cross-connections like a household booster connection and is testable and maintainable with standard test cocks. Higher-hazard devices, such as a reduced pressure principle or a pressure vacuum breaker, are not required for this scenario, and while an air gap is highly protective, it isn’t practical or typically used on a service line with a portable meter.