For stop valves 8 inches or larger, what size must the bypass be?

The requirement for a bypass on stop valves that are 8 inches or larger is to ensure proper operation and maintenance of the valve. A bypass allows for the flow of fluid around the valve when it is closed, which is crucial in large piping systems to maintain system pressure and ensure that operations can continue without interruption.

A 3/4" Sch 80 bypass is specifically suitable for this task as it balances a sufficient flow rate while maintaining compatibility with the larger stop valve size. The schedule 80 designation indicates that it has higher pressure ratings compared to lower schedule pipes, ensuring that it can handle the operational demands present in high-pressure systems without risk of failure.

Using a bypass that is too small could restrict flow and not provide adequate circulation or could increase the pressure in the bypass itself, potentially leading to safety issues or system inefficiencies. Conversely, a bypass that is excessively larger than the required size could be wasteful and introduce unnecessary complexity in the piping system.

Therefore, a 3/4" Sch 80 bypass is the optimal choice based on industry standards and practical functionality for stop valves of this size.