They install, modify, and repair systems by setting up system routes, placing and cutting route openings, installing hangers at proper pitch and elevation, and determining and installing such things as risers, branch outlets, expansion joints, pumps, gauges, and pressure regulators in the combination needed to ensure the proper operation of the systems. The pipefitters also install equipment by planning and completing the routing and placement of systems leading to the equipment, determining and placing the equipment at the proper elevations and points in the systems, and joining, sealing, and testing systems and equipment for proper pressures, leak-free joints, and operation.