Which of the following is NOT a type of backflow prevention device?

A pressure gauge is not a type of backflow prevention device. Backflow prevention devices are specifically designed to prevent the reverse flow of contaminated water into the potable water supply, ensuring public health and safety. The double check valve assembly, air gap, and reduced pressure backflow preventer all serve this critical function in different ways.

The double check valve assembly consists of two check valves arranged in such a way that if one fails, the other can still prevent backflow. The air gap is a physical separation between the water supply and the potential contaminant, effectively preventing backflow by gravity. The reduced pressure backflow preventer uses a valve and pressure sensors to protect against backflow scenarios, making it often more sophisticated in preventing contamination. These devices are essential in various plumbing applications to maintain the integrity of drinking water.

In contrast, a pressure gauge is primarily used to measure the pressure of a liquid or gas within a system and does not provide any mechanism for preventing backflow. Therefore, it is correctly identified as not being a type of backflow prevention device.