The Moorish shaped pump house bearing the Harrington 'h' cipher houses a four cylinder pump by John Harrison of Derby that delivered water from the lake to a water tower in the courtyard and from there to the fountains in the garden.
A corresponding supply pipe provided irrigation to the extensive green houses and also a vinery within the walled garden.
Inside the castle there was originally a water powered lift that utilised the hydraulic pressure from the head of water in the tower to carry such diverse things as people, property and coal to the different levels within the castle serving the various rooms.
The design of the unusual waterwheel is attributed to the Earl of Harrington. It is a rather unique device as it is a breastshot water wheel operating on no more than a foot of difference in water level. The water ran down from the lake to the waterwheel.
It was restored by Dorothea Restorations assisted by Derbyshire Archaeological Society and Leicester Industrial History Society in the mid-1970s but is currently no longer in working order.