For valves that are 8" or larger, what is the required size of the bypass?

The requirement for the size of the bypass for valves that are 8 inches or larger is specified to ensure that there is adequate flow capacity to maintain safe and efficient operation. A bypass is essential in high-pressure systems as it allows for maintenance and inspection of the valve without having to shut down the entire system. In this case, 3/4" Sch 80 is the optimal size for the bypass because it provides a proper balance between sufficient flow rate and manageable pressure drop across the system. This size ensures that maintenance can be performed effectively while minimizing the impact on system operations.

Using a bypass smaller than 3/4" could lead to inadequate flow, potentially causing pressure build-up or flow restrictions. At the same time, a bypass larger than 3/4" may not align with standard practices for valves of this size, which are typically specified for efficiency and cost-effectiveness in the design of high-pressure piping systems. Thus, the specification of 3/4" Sch 80 for the bypass provides both functional and regulatory compliance for valve operation in high-pressure systems.