Which of the following defines an acceptable mechanical fitting?

An acceptable mechanical fitting is characterized by its ability to securely join pipes while maintaining proper function and integrity of the system. A clamp design serves as a reliable method for securing pipes together. This type of fitting allows for easy installation and removal, making it practical for various situations in plumbing and distribution systems. Furthermore, the clamp can adjust to accommodate slight variations in pipe diameters, making it versatile for different applications.

In contrast, the other options may not fully encapsulate the criteria for a mechanical fitting. A rubber seal, while essential for ensuring a watertight connection, is not a mechanical fitting on its own as it may lack the structural integrity to maintain alignment under pressure. Total isolation typically refers to stopping the flow of water rather than connecting pipes, which does not pertain to the definition of a fitting. A threaded connection, although a form of mechanical fitting, may not always be considered acceptable due to potential issues with sealing and integrity over time, especially under certain conditions where movement or vibration is present.