Imagine you have a natural stream running through a low-lying area on your farm. It’s a great source of fresh water, only you really need it to irrigate some crops sitting at a higher elevation. The area is quite remote from fixed utilities, complicating the problem.

Your first thought might be to grab a commercial off-the-shelf pump of some sort, along with a fancy solar power system to provide the necessary power to run it. But what if there were a type of pump that could do the job with no external power input at all? Enter the hydraulic ram pump.

The hydraulic ram pump stands as one of the most elegant examples of appropriate technology, converting the kinetic energy of flowing water into enough pressure to lift a portion of that water to heights that seem to defy gravity. This ingenious device requires no external power source and very little maintenance, making it a perfect solution for pumping applications in remote areas where it’s otherwise inconvenient to supply a pump with electricity or fuel.

At its heart, the hydraulic ram pump exploits a phenomenon known as water hammer, the same effect that causes your pipes to bang when you quickly shut off a faucet. When flowing water is suddenly stopped, its momentum creates a pressure wave. When it comes to your pipes, you hear this rattling, hammering sound that is mostly just annoying. However, that pressure spike can actually instead be harnessed to do useful work—like pushing water uphill. It just requires some smart valving to do so.

The pump consists of just a few key components: a drive pipe that channels water from a source, a waste valve that normally allows water to flow freely, a delivery valve leading to the pump’s output, and an air chamber that acts as a pressure accumulator. These parts work together to create a self-sustaining pumping action.

The operation of the pump begins with water flowing down the drive pipe from a source that sits higher than the pump, such as the flow from a river or stream. Initially, the waste valve is open and water flows freely through it. As the flow velocity increases, the waste valve begins to rise due to the drag of the water flowing through it. Eventually, the valve rises to the point where it is completely shut, suddenly stopping the flow of water. This sudden halt causes water hammer, where the kinetic energy of the flowing water is converted into a powerful pressure spike that forces the delivery valve open, pushing water up through the pump outlet. Eventually, the pressure drop following the water hammer event causes the waste valve to reopen and the delivery valve to close, allowing the cycle to begin anew.

Some pumps add a pressure chamber to the system, where the pressure spike leads to a vessel, compressing the air trapped inside. The compressed air acts like a spring, maintaining outflow pressure even after the initial water hammer effect subsides. This can improve flow and reduce strain on components of the pump by evening out the sharp pressure spikes when the waste valve closes.

This being Hackaday, we should mention that this is a lot like a step-up DC-DC converter, with an inductor playing the role of the water-filled pipe, providing intertia, and a diode and a smoothing capacitor playing the parts of the check value and air vessel. In electrical step-ups, the waste valve is usually a MOSFET to ground, and its driven electronically, rather than being slammed shut by the water hammer.

A hydraulic ram pump effectively takes a rapid flow of water at low pressure and delivers a low-speed flow at high pressure, allowing water to be readily delivered to a tank or output at higher elevation than the source. The ratio between the vertical fall of the drive water and the height to which water is lifted determines the amount of water reaching the output. For example, if the water source is 1 meter above the ram pump itself, and the delivery pipe is 10 meters above the pump, just 10% of the water will be delivered to the output with the other 90% passing out through the waste valve. Ultimately, though, this is generally considered an acceptable trade-off for a pump running from a natural water course with no external power input, with the waste valve outflow simply returning to the river or stream the pump is installed in. A hydraulic ram pump can be left running for a great deal of time to deliver more water and irrigate an area or fill a tank, even if the instantaneous flow rate is low. After all, you’re not paying for any power to run it!

Hydraulic ram pumps are popular where it’s desirable to pump water to some greater height without the need for an external power source.

Today’s hydraulic ram pumps find applications ranging from rural water supply systems to irrigation projects in developing countries. The hydraulic ram pump can prove useful in most any situation where it’s desirable to pump water to high elevation with no external power input. Ultimately, the hydraulic ram pump represents sustainable technology at its finest. It’s a clean, undisruptive way to harness natural energy to do useful work. What’s more rewarding than that?

Featured image: “Hydraulic Ram” by [Gutza] and [Sonett72].