What is a wet return?

A wet return refers to a piping arrangement that is designed to convey condensate below the normal operating water line (NOWL). In steam heating systems, when steam is used to heat spaces, it condenses back into water after releasing heat. This condensate must return to the boiler for reheating; thus, the wet return pipes are crucial for transporting this condensate back through the system.

When these pipes are below the normal operating water line, they remain filled with water, allowing for efficient drainage and ensuring that the condensate can flow back to the boiler without the risk of air locking or creating a vacuum. This is important for maintaining the efficiency of the steam system and preventing potential damage that could occur if the condensate were not properly returned.

In contrast, the other options describe scenarios that do not accurately represent the function or characteristics of a wet return, making this the correct and relevant definition within the context of steamfitting and heating systems.