Which of the following is NOT a standard method for joining pipes?

Grooving is not considered a standard method for joining pipes in the same way as the other options listed. While it is a method used in certain pipe systems, such as in some mechanical piping installations, it is not a widely recognized technique universally across diverse piping methods.

Welding involves melting the base materials and allowing them to fuse together as they cool, creating a strong, permanent bond that is common in various industrial applications. Soldering is a low-temperature process used primarily with metal pipes, where a filler metal is melted and flows into the joint, solidifying upon cooling to create a reliable joint, particularly in plumbing and electronics. Threading involves cutting spiral grooves into the ends of pipes, allowing them to be screwed together, which is a standard method particularly for joining pipe sections in plumbing and gas lines.

In contrast, grooving typically refers to a method where a groove is cut around the pipe's circumference to allow for a coupling mechanism, which may not be as universally utilized, defining it as not a standard method for pipe joining.