After brass or black iron pipe has been cut, it should be:

When brass or black iron pipe has been cut, the proper procedure is to ream the edges. Reaming involves smoothing out and removing any burrs or sharp edges that may have formed after the cut. This process is crucial as it ensures a smooth interior and exterior surface on the pipe, which helps prevent any potential leaks when fittings are installed. A clean edge allows for a proper seal between the pipe and fittings, promoting the effective flow of liquids or gases through the piping system.

This technique also minimizes the risk of damage to seals or connectors when the pipes are joined together. Using a reamer improves the overall integrity of the connection. Keeping in mind that performance and safety in sewage treatment are paramount, reaming is an essential practice to ensure lasting and functional installations in piping systems.

Regarding the other options: counterboring involves creating a recess in a material, which is not applicable in this context. Countersinking is used to create a conical hole for flat-head screws, which is not relevant when dealing with the edges of cut pipe. Squaring is about making the ends of the pipe perpendicular to the length, which is also insufficient for ensuring smooth and clean edges necessary for joining. Thus, reaming is clearly the correct technique to apply