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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 specialized high-
pressure water supply.
Because water is incompressible,
the valve gear of water engines is
more complicated than that used in steam engines, and some water
engines even had a small secondary engine solely to power the operation of their valves. Closing a valve too quickly can cause very large pressures to result, and pipework to explode (a phenomenon similar to water hammer).
A prerequisite for the correct
function of the water engine was
sufficient pressure in the water
pipes. In times of high water
consumption (before or after work) the water pressure was often insufficient. In hard winters, in which the water pipes often froze,the water engine could not be used.