Why must all pipe be reamed to the full inside diameter?

Reaming all pipe to the full inside diameter is essential primarily to prevent turbulence in the flow of fluids through the pipes. When pipes are cut, especially with certain tools, the edges can become jagged or cause a restriction in the pipe's interior. This narrowing or irregular surface can disrupt the smooth flow of liquids or gases, leading to turbulence, which can create pressure drops, increase wear on the piping system, and reduce overall efficiency.

By ensuring that the inside diameter is consistently reamed to its full size, the flow of the medium is unimpeded, minimizing the likelihood of cavitation, turbulence, and the associated energy losses. This practice is particularly important in plumbing and piping systems where consistent flow rates and pressure are paramount for functionality and safety.

While there may be other potential benefits to reaming, such as improving aesthetics or enhancing structural integrity, these are secondary considerations compared to ensuring a smooth and efficient flow within the system.