Assists journeyman level pipefitters in laying out, fabricating, assembling, installing and maintaining piping systems, pipe supports, fixtures, and related hydraulic and pneumatic equipment for steam, hot water fixtures and equipment for steam, hot water, heating, cooling, lubricating, sprinkling and production and processing systems. Installs and maintains refrigeration and air conditioning systems, including compressors, pumps, meter, pneumatic and hydraulic controls and piping, Test piping systems for leaks by increasing pressure in pipes and observing gauges attached to pipes for indication of leaks.