What is the minimum unrestricted drain opening required for gauge glass drains?

The minimum unrestricted drain opening required for gauge glass drains is 1/4 inch. This size is specified to ensure that any potential blockages or buildup in the drain can be adequately cleared and that the gauge glass can be drained properly without risk of failure or malfunction due to insufficient drainage. A larger opening reduces the possibility of clogging and facilitates reliable operation of the gauge glass, ensuring accurate readings of the fluid levels within the system. The specification for a 1/4 inch opening reflects industry standards designed for safe and effective operation in pipefitting applications. This diameter strikes a balance between preventing blockages and ensuring that the function of the gauge glass is not compromised.