Hydraulic Ram Pumps

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The Montgolfier brothers, better known for their invention of the hot air balloon, were the first to develop the hydraulic ram pump, or hydram, in France in 1796. Hydrams are automatic pumping devices that utilise a small fall of water to lift a fraction of the supply flow to a much greater height. The main virtue of the hydram is that its only moving parts are two valves. It is, therefore, a very simple mechanical device that requires very little maintenance and has a long operational life.

Hydrams are ideal for pumping water in areas that do not have electricity, but have a steady source of falling water, such as the mountains and hills. It was used extensively by the British in the remote and hilly regions of India to pump water to residential quarters. These pumps are silent and eco-friendly as they do not use electricity or fuel, and instead use gravity to lift water. In addition, the outlet of the hydram pump can be fitted to water sprinklers for irrigation.


How a Hydram Works?

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The pump uses a phenomenon called ‘water hammer’. Overall efficiency can be more than 50 per cent, usually aggregating between 60 per cent and 80 per cent.

Water from the falling source closes the waste valve and opens the valves for the water to enter the air chamber and the outlet pipe. The air in the air chamber gets compressed till a point when the pressure exceeds the inflow pressure. It’s at this point that both gravity and the pressure of the compressed air force the valves to close. The pressure built up in the chamber is released by forcing the water out of the chamber to the exit pipe. This process is repeated again and again to deliver the water to the desired height.

The air chamber is the most vital component of the system. If the air chamber fills with water completely, it becomes completely ineffective and can also get fractured by the hammer force. There is a tendency of air to get dissolved in water under pressure.

Different hydrams have different mechanisms to overcome this problem. The simplest solution requires the user to stop the hydram occasionally and drain the air chamber by opening two taps, one to admit air and the other to release water. Another method is to include a sifting valve, which automatically allows the air to be drawn into the chamber when the air pressure drops below the atmospheric pressure.


Hydrams are mostly intended for water supply in hilly or mountainous areas that require small flow rates delivered to high heads. The pumps come in different sizes based on requirements. For example, a 50mm X 20mm pump means an inflow of 50mm water pipe and outflow of 20mm water pipe. There is a complicated formula for calculating the discharge and height delivered based on the inflow, height or drop in water and desired outflow. For example, a 50mm X 20mm pump drop of 5 metres can easily lift 11 litres per minute to a height of 20 metres.

References and Useful Websites

  • Hydraulic Ram Pumps: A Guide to Ram Pump Water Supply Systems by T.D. Jeffery, T.H. Thomas, A.V. Smith, P.B. Glover, P.D. Fountain
  • An Analysis of the Hydraulic Ram by H.W. Iversen
  • A Hydraulic Ram for Village Use—Volunteers in Technical Assistance by E.W. Kindel
  • Renewable Energy Sources for Rural Water Supply in Developing Countries by Hofkes and Visscher
  • A Manual on the Hydraulic Ram for Pumping by S.B. WaterWatt
  • Lifewater canada
  • How does a hydraulic ram pump work?
  • Home-made Hydraulic Ram Pump
  • Ram Pump Programme
  • Hydraulic Ram Pumps