Does anyone know a device that incorporates this principle? Process is as follows:

  1. You get a lot of water at low to mid pressure (let's say 1 bar)
  2. A device D converts the work that 1 liter of water performs at one bar to 0.1 liters of water at 10 bars. D does not perform any work powered by an external electrical source (control electronics is fine, it's not 1910. We have solar power).
  3. Watering is much more fun and you can spread water over large distances while sitting down (this is a joke but the rest is totally serious).

My gut feeling says that this must be a principle identical to a DC-DC buck/boost converter. Does anyone know about such a device?

The well-known "self-powered" water control system is the lawn sprinkler and its modern grandchildren. They control the velocity vector, so...

The Tesla valve also comes to mind (as a component, at least).

Edit: Nowadays, there is a Wikipedia page for (nearly) everything: https://en.wikipedia.org/wiki/Hydraulic_analogy. I think the main idea I missed is a flywheel. But anyway, my question is about an existing device of any kind.

  • 2
    $\begingroup$ I think what you're looking for is a "pump". $\endgroup$
    – Hot Licks
    Jul 14, 2023 at 20:43
  • $\begingroup$ You cannot "convert" 1 liter of water to 0.1 liter. For every liter that goes in, exactly one liter must flow out. You can have 0.1 liter flow out at a higher pressure, but the other 0.9 liter must go somewhere. The main way it's different from your DC-DC converter example is, in the electronic circuit, the current always flows in closed loops. But in your Device D, either you must run a pipe all the way back to the water company to return the 0.9 liter, or else you're going to "waste" it on your lawn. $\endgroup$ Jul 14, 2023 at 21:20
  • $\begingroup$ @HotLicks: It is a kind of pump, but what is its name? $\endgroup$
    – zonksoft
    Jul 14, 2023 at 21:27
  • $\begingroup$ @SolomonSlow: I am aware of this, that's a perfectly alright property of D and I didn't make any requirement in this regard in my question. Thank you for pointing it out! $\endgroup$
    – zonksoft
    Jul 14, 2023 at 21:28
  • 2
    $\begingroup$ You might have in mind a hydraulic ram. This uses the kinetic energy of flowing water to force a (much smaller) volume of water under pressure through a pipe. $\endgroup$ Jul 14, 2023 at 21:44

1 Answer 1


I was asked if I'd like to post an answer based on my comment on hydraulic rams, so I'm having a go, though I'm no expert. You can find diagrams and videos on the internet.

In a hydraulic ram, water rushes down a pipe from a higher level reservoir because it is allowed to escape through an open valve (A) at the bottom end of the pipe. The valve is suddenly shut and another valve (B), also near the bottom of the pipe is opened, so that rather than being stopped dead, the water is allowed to rush into the bottom of a sealed chamber. The rush of water compresses air in the chamber into a space at the top of the chamber. The pressure forces water out of a relatively thin 'output' pipe that goes from the bottom of the chamber to some place, no doubt at a greater height than the reservoir, where it is needed. The cycle repeats.

The system is self-acting; the valves are opened and closed by pressure differences.

Note that much more water per cycle is allowed to escape via valve A than goes usefully through the output pipe. But this doesn't imply that as big a fraction of the water's energy is wasted: the output pipe may well take the water (albeit less of it) to a considerably greater height than the reservoir from which it came.


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