How to Build a Float Pump

Learn how to extract useful power from a small, slow stream.

| January/February 1977

Charles Bertram asked if anyone knows of a way he can life water from a small spring to a trickle irrigation tank for apple trees situated 65 feet higher up a slope. Perhaps the float pump — which fills a niche between the familiar hydraulic ram and the waterwheel — is just what Mr. Bertram needs. This handy-dandy little device combines pump and prime mover into one assembly ... and can operate on as little as six inches of head!

I'm not really sure of the float pump's origin, although I think it was developed around the turn of the century. I first ran across the idea when I was told about one of the units that had been installed near Walton (north of Lexington), Kentucky. As a result, I sat down and designed the pump as seen in the Image Gallery "from scratch" with the typical semiskilled back-to-the-lander in mind.

No, this probably is not the way I'll build one of these little rigs for my own farm (since I own a fairly elaborate machine shop and research lab). But the one shown here should work, and should be fairly easy to build.

Building a Float Pump

The largest component (the casing) of this pump is a 55-gallon drum with a removable head. Such a barrel — which is easy to obtain at low cost almost any place in the world — establishes the maximum usable head of the finished float pump at approximately 2.5 feet of water. The largest float that we can reasonably expect to use in such a casing will have a diameter of 20 inches, and I've chosen to make that float 10 inches in height.

(The pump's float, as I'm sure you realize, should come as close to completely filling the inside of its casing as possible ... without actually contacting the barrel's wall. Too much clearance simply wastes water without improving either output pressure or flow. Too little can cause the float to "hang up" and slow or completely stop the pump's action.)

Since the float doesn't actually wear against its casing, it can — for the most part — be made of fairly fragile materials. Consider a block of styrofoam (which can be worked with a saw, knife, or even a hot wire!) sandwiched between top and bottom plates of aluminum or steel. The entire assembly can then be painted with melted paraffin to decrease its absorption of water and, thereby, improve its buoyancy.

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