Which backflow assembly consists of two check valves and lacks a relief valve?

The Double Check (DC) backflow assembly is designed to protect the water supply by using two check valves arranged in series. This configuration prevents backflow, ensuring that water cannot flow back into the potable water system from the non-potable side. The absence of a relief valve distinguishes it from other assemblies, such as the Reduced Pressure (RP) assembly, which includes a relief valve as a critical component for additional protection. The two check valves in a Double Check assembly effectively create a barrier against potential contamination, making it well-suited for low to moderate risk applications where the environmental hazard is not significant.

In contrast, the other options involve different mechanisms and functionalities. For instance, an Air Gap provides a physical separation between the water supply and potential contaminants. The Back Pressure assembly similarly addresses specific backflow scenarios but is not structured like the Double Check assembly. Thus, the defining characteristic of the Double Check backflow assembly, with its pair of check valves and lack of a relief valve, makes it the correct choice in this context.