Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

Though not quite the same, I have several "gravel suckers" that I use for prospecting, panning and sluicing, that work on pretty much the same principle, though they don't possess a flapper valve to exchange water from the lower to the upper chambers. On my suckers, it is just a partial vacuum pump that pulls in and holds momentarily, then expels out the same way it came in, whether through simple gravity, or with quite a bit of force by plunging, if desired. Works very well once you get the hang of it and the timing of the "pause" at the top of the stroke, before the contents of the sucker start falling out. Quite impressive the amount of material one of these is capable of moving, and yes, I have often found gold using them!

I have also used a very similar device to "pump" sand from the bottom of a shallow well, which does make use of a flapper "foot" valve to allow disturbed material from the bottom of the well to get trapped above the "valve" and thus is able to be extracted from the well.

As Jan says ... the basic principles behind this form of pump have been known and used for Millennia, both on land and at sea!