We introduce a new simulation tool designed for experimental training research and present results from an experimental study conducted to validate it. The Waste Water Treatment Simulation (WaTr Sim) is a computer-based simulation of a complex process control task characterized by high dynamics, interrelatedness, feedback delays, and opaqueness. It includes start-up and shut-down procedures, monitoring, and control. In a training experiment (N = 48) WaTr Sim was evaluated and compared to a well-studied process control simulation called Cabin Air Management System (CAMS). Diagnostic performance on CAMS was especially related to those performance elements in WaTr Sim that required consideration of and adherence to fixed and contingent sequences. WaTr Sim has unique features, such as the possibility of creating scenarios to study instance-based learning or transfer tasks. Findings indicate that the simulation can be employed in training experiments to analyze various demands of process control tasks.