Which of the following is NOT considered a miscellaneous piping in a boiler?

In the context of boiler systems, miscellaneous piping typically includes components that are not directly part of the main operational functionality of the boiler itself, but still play a role in its overall operation and safety. Drains, vents, and gauge glass piping are all vital components that help manage water levels, release excess pressure, and provide visibility into the boiler's water level, respectively.

Steam generator piping, however, is integral to the boiler's operation as it handles the steam produced during the heating process. It is central to the boiler's function of generating steam for heating or power generation, making it a core component rather than a miscellaneous one. This distinction is what leads to steam generator piping not being categorized as miscellaneous, as it directly facilitates the primary purpose of the boiler system.