Water engine

The water engine is a positive-displacement engine, often closely resembling a steam engine with similar pistons and valves, that is driven by water pressure. The supply of water was derived from a natural head of water, the water mains, or a specialised high-pressure water supply such as that provided by the London Hydraulic Power Company. Water mains in the 19th century often operated at pressures of 30 to 40 psi, while hydraulic power companies supplied higher pressure water at anything up to 800 psi.

The term water motor (German: Wassermotor) was more commonly applied to small Pelton wheel type turbines driven from a mains water tap (e.g. Whitney Water Motor), and mainly used for light loads, for example sewing machines.

In the nineteenth century, the terms hydraulic motor and hydraulic engine often implied reference to any motor driven by liquid pressure, including water motors and water engines used in hydropower, but today mentions of hydraulic motors, unless otherwise specified, usually refer more specifically to those that run on hydraulic fluid in the closed hydraulic circuits of hydraulic machinery.