| Chapter 1: | Water Supplies |
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work when that momentum is harnessed. In addition to being a potential source of mechanical power, which is considered in chapter 5, waterpower from a river was often directly utilised to pump a small part of its flow to a considerable elevation. Even when the river course was well below the level of the house, a ram pump could pump this small part of its flow to a roof-space storage cistern that provided gravity-fed water supplies throughout the house for baths, flushing water closets, and other nondrinking purposes. It is possible that the name of this simple and highly efficient pump came from the medieval battering ram.27 The action is similar in that the swiftly moving column of water in the supply pipe is suddenly arrested by the beat valve and rebounds just like a battering ram attacking a closed door. Although invented by John Whitehurst of Derby in 1772, it was not until Pierre Montgolfier incorporated a snifter valve in 1816 that the hydraulic ram pump was made completely automatic. Montgolfier appears to have been working on such pumps for many years before this, as, when Maria Edgeworth visited him in Paris at the beginning of 1803, she saw his “bélier for throwing water to a great height”.28 Josiah Easton began the manufacture of ram pumps in England in 1820.29
Plate 8 is a drawing of the cross section of a hydraulic ram pump, indicating the position and names of the principle parts. Initially, the delivery and beat valves are closed, and the supply pipe is full of water provided from a source above the level of the pump. When the beat valve is manually opened by pressing it downward, the water in the supply pipe rapidly runs to waste. Releasing the beat valve allows the swiftly moving water to slam the beat valve shut. This sudden arrest of the flow causes the mass of water to bounce back and produces a dramatic pressure increase, thus forcing open the delivery valve and admitting some of the water under pressure into the air chamber above. The bounce back of the water from the beat valve also creates a partial vacuum under it, allowing the outside atmospheric pressure to reopen the beat valve, and allows the supply water to run to waste again. With the water pressure thus reduced, a temporary partial vacuum occurs beneath the delivery valve. Before it closes, a small quantity of air is admitted via the snifter valve and, being lighter than water, rises to the top of the air chamber.