Ram pumps have been around for many decades and are popular for two reasons:

  1. They need no external source of power -- the force of moving water gives them the power they need
  2. They are extremely simple, with just two moving parts.
The basic idea behind a ram pump is simple. The pump uses the momentum of a relatively large amount of moving water to pump a relatively small amount of water uphill.

To use a ram pump, you must have a source of water situated above the pump. For example, you must have a pond on a hillside so that you can locate the pump below the pond. You run a pipe from the pond to the pump. The pump has a valve that allows water to flow through this pipe and build up speed.

  • Once the water reaches its maximum speed this valve slams shut.
  • As it slams shut the flowing water develops a great deal of pressure in the pump because of its inertia.
  • The pressure forces open a second valve.
  • High-pressure water flows through the second valve to the delivery pipe (which usually has an air chamber to allow the delivery pipe to capture as much high-pressure water as possible during the impulse).
  • The pressure in the pump falls. The first valve reopens to allow water to flow and build up momentum again. The second valve closes.
  • The cycle repeats
The delivery pipe can rise some distance above both the pump and the source of the water. For example, if the pump is 10 feet below the pond, the delivery pipe might be as high as 100 feet above the pump.

You can see that the one big disadvantage of a ram pump is that it wastes a lot of water. Typically about 10% of the water it consumes actually makes it up the delivery pipe. The rest flows out of the pump as the water builds momentum.

There is nothing magic happening in a ram pump. A different design that accomplishes the same thing might look like this:

  • Water flows downhill from the pond and drives a water wheel
  • The water wheel is connected to a conventional shaft-drive pump (a reciprocating pump, a centrifugal pump, etc.)
  • The pump moves water uphill.
This design has more moving parts, but it accomplishes the same thing and has the advantage that it scales to any size very easily. The idea of using the energy of flowing water has been around for a long time!

Here are several interesting links: