The sheer scale of the Pumping Engine makes it difficult for the visitor to see the whole operation of the engine working at once; this is in part due to the "bob wall", the central dividing wall across the ground floor. This wall supports the beam on an axle 12 inches in diameter. The beam connects the engine to the pump and consists of two single castings, 33 feet long, side by side and weighing a total of 27 tons.
The steam cylinder is fifty inches in diameter and is over 10 feet tall, giving a stroke of over 9 feet.
Steam is produced by two locomotive type boilers in the neighbouring boiler house. The boilers were built by Hawthorne Leslie & Co., Newcastle upon Tyne as part of a subcontract of ten from the Midland Railway Company and can produce steam at 40psi. The original boilers are thought to have been the Lancashire type, as some remaining fixtures in the boiler house point to this.
The pump works by both the suction and pushing of water. As the 15 ton plunger rises, a vacuum is created and water is sucked in through a non-return valve into the pump chamber. When the plunger reaches the top of its stroke, the chamber will contain just under 4 tons of water (approx 800 gallons). The valves on the engine change and allow the plunger to descend under its own weight, thus forcing the water through the outlet valve and up into the canal. Photo