Which valve is used as the flush valve in a type 4 system?

The correct answer identifies the specific flush valve used in Type 4 systems, which is the 136AF-5B. This valve is designed for flushing purposes, helping to clear out contaminants and debris from the system, ensuring optimal operation and reducing the risk of clogs or impairment in water and fuel systems. The choice of a valve in this context is critical, as each type and model of valve has specific functions and characteristics tailored for various applications within these systems.

For instance, flush valves must be capable of handling the pressures and flow rates typical of Type 4 systems, as well as being resistant to the chemical properties of the fluids they will encounter. The 136AF-5B meets these criteria, making it the appropriate selection for a flush valve.

The other options, while they may belong to similar categories of valves, do not have the same specifications or functionality designated for use specifically as a flush valve within the context of a Type 4 system, which is why they are not the correct answer in this scenario.