What is a key requirement for installing a Double Check backflow prevention assembly below grade?

For a Double Check backflow prevention assembly installed below grade, it is essential that the test cocks are plugged with non-ferrous material. This requirement is pivotal because it prevents any potential contamination from entering the potable water supply through the test cocks, which are critical points in the assembly for monitoring and testing the backflow prevention system. Using non-ferrous material ensures that there is no corrosion or reactions with the water that could compromise the system’s integrity.

Non-ferrous materials do not rust and are more resistant to corrosion, making them suitable for plumbing applications where they may be exposed to water and various environmental conditions. This requirement ensures the longevity and reliability of the assembly, promoting public health and safety by maintaining the effectiveness of the backflow prevention measures.

Other options provided do not align with the requirements typically outlined for backflow prevention assemblies. For instance, the requirement that test cocks must be a specific material, or that they must be a certain height above grade, does not pertain to installations below grade and might even compromise their operational integrity if not followed according to code. Thus, the accurate use of non-ferrous material in plugging test cocks is a clear standard ensuring the safety and functionality of the backflow prevention system.