Ram Pump

A ram pump lifts water uphill using nothing but the fall of the water that drives it. It has no motor, takes no power of any kind, and its two moving parts are valves. Water runs down a long pipe from a source above, and once moving fast the first valve slams shut. The shock of that stop - the knock a house pipe makes when a tap is closed hard - forces a small share of the water past the second valve into a sealed chamber of trapped air, which cushions the blow and pushes that share up the delivery pipe. It repeats twenty to a hundred times a minute as long as water keeps arriving.

Fall is the whole requirement, and it has to be in the land already. About 0.9 m (3 ft) of drop from source to pump is the practical minimum, with 10 litres a minute (2.5 gallons) of flow the floor beneath that, but fall is a multiplier, not a threshold: going from 1 m of head to 10 m can raise delivery as much as twentyfold. The pipe feeding it is part of the machine, at least five times the vertical fall long. Most of the driving water is never lifted: it leaves through the first valve by design, and 30 to 60 per cent of the energy reaches delivery.

What comes out is a small flow that never pauses, so a ram fills a tank uphill rather than answering a tap, and the irrigation, stock water or fire reserve it allows waits on that tank. Three things go wrong. The trapped air slowly dissolves into the water, and a chamber that fills completely can fracture the pump with the shock it was there to absorb, so letting air back in is the routine job. The pump must sit above flood level, since the waste valve stops working the moment it goes under. A mistuned valve breaks nothing and delivers nothing. Otherwise the work is clearing the intake strainer and keeping the discharge draining away, since a ram throws out more than it lifts. Running cost is nil and the machine can last thirty years or so.