What is the primary purpose of using a cap or plug when disconnecting a drain?

Using a cap or plug when disconnecting a drain serves the primary purpose of sealing the disconnection. When a drain line is opened, it creates an opening that can allow air, debris, and potentially harmful substances to escape or enter the system. By sealing the disconnection with a cap or plug, the integrity of the drainage system is maintained, preventing unwanted materials and gases from escaping into the environment. This is critical for maintaining hygiene and preventing foul odours from emanating from the open drain, which also ties into the need for proper drainage, but the focus here is on the sealing aspect.

While the other choices may touch upon related issues, they do not capture the core function of a cap or a plug in this context. The cap or plug's role is specifically to close off the connection and keep the system secured and properly sealed during any maintenance or repairs. This ensures that when the drain is reconnected, it can function effectively without any leaks or contamination risks.