Identify the purpose of a steam trap.

A steam trap's primary function is to discharge condensate while preventing steam loss. When steam is used in heating systems, it undergoes a phase change and turns back into water, known as condensate. This condensate must be efficiently removed from the system to maintain proper heat transfer efficiency and prevent water buildup that can lead to water hammer or other system issues.

The steam trap allows condensate to escape while creating a barrier that keeps steam in the system. This ensures that the energy in the steam is utilized effectively for heating rather than being wasted. The trap automatically opens to release the condensate when it accumulates but remains closed to steam, maintaining the pressure and temperature necessary for optimal system performance.

In contrast, maintaining boiler water levels pertains to the operation of the boiler itself, ensuring that the correct amount of water is present for steam generation. Converting water into steam describes the function of the boiler, not the steam trap. Filtering impurities is a process more relevant to steam quality management, likely involving other equipment such as filters or separators, rather than the steam trap's primary role.