New Dawn Engineering has designed many ram pumps (some shown on the right). Ram pumps pump water uphill without electricity or powered engines. They simply use the water power created by a vertical fall in a river or spring over a slope of about 1 in 5.
There are two main components of a ram pump: the waste valve and the delivery valve. They are both specialized types of check valve (non-return valve). The waste valve allows water to accelerate down a steel pipe and closes suddenly. This creates a hydraulic shock wave which generates high pressure (water hammer). The pressure pushes some of the water in the pump body past a closed delivery valve seal. The seal opens as long as the water pressure in the pump body is higher than the pressure in the air chamber above it. The pressure is high enough to push the water up a pipeline some considerable vertical and horizontal distance. There are only two moving parts.
There is a theoretical limit to the pressure which can be generated by suddenly stopping the moving water trapped in the drive pipe. It is about 153 times the water velocity. In the real world it means that if the water is moving 1 meter per second in the pipe, about 120 metres of lift can be generated, the rest being lost to various inefficiencies. It is possible to make ram pumps which can generate 150 metres of lift. They tend to be large as it takes a great deal of power to pump a meaningful volume of water at that pressure.
The basic equation for calculating the potential of a ram pump site is:
Litres per second of water available in the stream multiplied by the drop in metres from the collection point to the pump times 0.7 divided by the vertical head to be pumped (to the tank) multiplied by 3600. This gives the output in litres per hour. The 0.7 figure is a guestimate. Low pressure pumps can exceed 85% efficiency, high pressure ones may be only 45%.
A detailed analysis is available from firstname.lastname@example.org. The data required are
Distance from collection point to the pump
Distance from pump to tank
Amount of water you want to be delivered
A computer program is used to facilitate the design process. The resulting suggestions will be emailed back to you.
The pump prices range from $220 to $1500 or more.
4 inch low pressure ram pump, Thembalihle, Mpumalanga Prov, South Africa, delivers over 30,000 litres/day to a 13 metre head:
40mm ram pump, side view:
This 6 inch pump set into more than 2 tons of concrete pumps 173 cubic metres per day to a 24m head:
Students from the Setsembiso Sebunye High School test a 3 inch pump destined for Chimoio, Moçambique: