Home Made Bilge/Boat Pump from PVC Pipe
Not sure if I ever showed this before, we've had some rain over the last month and its been getting a work out emptying our two moored boats. It's quite relaxing being out of bed in one of the boats at 2.00am working this pump in the pitch black

I've been meaning to make a steam accessory pump on the same principle, but still haven't gotten around to it yet -
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https://youtu.be/CLJQ7KryI-M
It’s amazing how well that works! You need to make a toy version identical to it
It’s amazing how well that works! You need to make a toy version identical to it 
Its a
really simple flapper valve mechanism Nick.
That´s pretty cool Jim, they´re certainly quite effective, for what they are.
Used one myself as a kid, to pump water from the creek to the cattle

Think the invention is thousand years old or more, at work we have large cylinder brass versions as "last stand" emergency pumps, and have seen a centuries old one with a twin halves wooden barrel tied together with leather straps on a museum as well.
Should someone not want to engage in a DIY project:
https://www.ebay.com/itm/143200386159?epid=24032227375
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!
Hello Jim,
Very simple and effective. Should be quick to replicate. All I'm missing is the boat.
But maybe this is something for my neighbour. He can then support his suction pump in pumping out his garage at high water. I had already suggested to him to exchange his car for a submarine. But always driving around in the garage is stupid.
These have always been popular here because the old timber inboard boats had floorboards and the pipe could fit through a hole in them to pump out right to the keel.
They were made out of gal downpipe when I was a kid, only lasted one year in saltwater so PVC pipe is a big improvement.
A beautiful example of how one used to achieve one's goal with the simplest of means. Today, expensive technology is often used for this.