Water that was used to drive the turbines exited the Pump Room through a stone arch tunnel to the tailrace on the east side of the building. The tunnel, built as a circular arch, is 14 feet across at its bottom, and 7 feet high at its center. The tailrace directed the turbine discharge water back to the canal that returned this water to the river. The stone archway at the mouth of the tunnel can easily be seen since being uncovered as part of the building stabilization project conducted in 2009–2010. 

A typical section  of cast iron pipe and also a section of the wooden stave pipe that was used later on are both displayed near the tailrace.