Abstract: This invention relates to a sampling system for collecting a sample in a sample cylinder having valves on both ends. The system includes an inlet line, a return line, a four-way valve, a level indicator and a sample loop including sample cylinder connections. After the sample cylinder is connected to the sample cylinder connections, the system and four-way valve allow the sample fluid to be selectively routed to flow in the inlet line, through the sample loop and sample cylinder and through the exit line or to flow in the inlet line and through the exit line, bypassing the sample loop.