In most sizes of pipe, what does Schedule 40 correspond to?

Schedule 40 is a widely used standard for the thickness of the walls of pipes, particularly in the context of plumbing and industrial applications. It corresponds to a standard type of pipe that is suitable for various uses, including residential and commercial applications. This standard is defined by the American National Standards Institute (ANSI) and is recognized in the industry for providing reliable and consistent pipe dimensions.

The term "standard" indicates that Schedule 40 pipe maintains a specific schedule thickness that balances strength and weight, making it versatile for many different installations. It is commonly available in various diameters and materials, including PVC, CPVC, and metal, making it a general choice for a variety of piping needs.

Other options, while they may refer to types of pipes or manufacturing methods, do not accurately reflect the definition that Schedule 40 provides in terms of pipe wall thickness and application. Therefore, it is clear that "standard" is the most appropriate term to describe what Schedule 40 corresponds to in most sizes of pipe.