How are fittings classified?

Fittings are classified based on multiple criteria including size, type, and construction material. This comprehensive classification allows for the proper selection of fittings depending on the application requirements and system specifications. Size refers to the diameter and dimensions of the fittings, which are vital for ensuring compatibility with the pipes they will connect to. Type refers to the specific design or function of the fitting, such as elbow, tee, or coupling, which determines how the fitting will be used within the piping system. Construction material is crucial as it defines the fitting's suitability for specific substances, environmental conditions, and pressure ratings, considering the different properties of materials like PVC, copper, or stainless steel.

In contrast, the other options fail to encompass the full range of criteria necessary for fitting classification. Focusing solely on diameter, construction material, or pressure and temperature neglects important aspects of how fittings are used and selected in practical applications. Proper classification not only ensures functionality but also aids in maintaining system safety and efficiency.