While Darren and I are always searching for simple ways to get our work done without fossil fuels, sometimes nifty solutions surface by accident. Using the WaterBuck Pump as an air compressor to pump up a tire was one of those unexpected discoveries. (This technique will work with any hand water pump capable of pressurizing a tank, as explained below.)

After filling our 40-gallon pressure tank for watering the vegetable gardens on a 95-degree day, Darren commented about the amount of compressed air at the top of the tank.

“You know, I bet I could fill a tire with this,” he said, pointing to the condensation line on the outside of the pressure tank. Water occupied most of the tank, but several inches of compressed air filled the top.

The next thing I knew, Darren was rummaging through spare parts in his workshop. As this is nothing new, I kept watering the garden. Minutes later, he returned with an air hose, chuck and fittings. To test his latest theory, he filled an inner tube with the compressed air.

The 14-inch inner tube filled in seconds, without expelling all the air from the tank. Even if the task required filling a vehicle tire to 35 PSI, it could be done this way.  We would simply drain the water from the tank (by watering plants, of course), and then pump up the tank again. After repeating the process, pressurized air is transferred from the tank to the tire – all without energy of any sort except human power.

Most homes with private wells have cold water pressure tanks. When the water is forced into the tank (by hand pumping or electric pump), the air above the water is compressed. This compressed air can be utilized.

As with any transfer of air from one vessel to another, the air will equalize in the containers. For example, if there is 50 pounds of air in Tank A and 0 pounds in Tank B (or a tire), the air pressure will equalize in each tank. So, to fill Tank B to 35 pounds, Tank A must be pressurized again to 50 pounds and repeated until tank B reaches 35 psi.

This small amount of compressed air would not be practical for operating pneumatic tools, but, in an emergency would be a quick, easy way to fix a flat. With a portable air tank, compressed air could also be transported to the field.

How to Use a Hand Pump as an Air Compressor

Any hand water pump that is capable of pressurizing a tank for indoor plumbing will work along with a pressure tank that has connections for air fittings. (A larger tank will hold more air than a smaller one.)

Remove the cap or plug from the top of the pressure tank and install fittings necessary for a quick-connect air coupling. Connect the air hose to the coupling. The end of the hose should have an air chuck  to fit your tire or tube valve stem.

Pressurize the tank by filling it as usual with your hand pump. Do not exceed the manufacturer’s recommended safe limit. We fill ours to 50 pounds of pressure (with 33 strokes of the WaterBuck’s handle). Now connect the air chuck to whatever you wish to inflate. That’s all there is to it.

The concept of pressurizing air with water is not new, but has been virtually forgotten since fossil fuels enabled humans to compress air mechanically, as John R. Hunt points out in a 1977 Mother Earth News story, Harness Hydro Power with a Trompe. Long before electricity, people would compress air with the help of falling water.

“For the homesteader or farmer with a small waterfall or a good-sized stream on his property, the trompe is a natural,” writes Hunt. “It offers a virtually inexhaustible supply of free compressed air … cool, dry air that can be used to operate a forge, drive machinery, or air-condition a house or barn in hot weather.”

Now, without a waterfall — just a hand water pump, pressure tank and muscle — you can compress air.

Video:  Well WaterBoy Products demonstrates how to use a hand water pump and pressure tank to compress air.  This can be useful when the compressor or power goes out and air is needed in a vehicle tire.  The WaterBuck Pump pressurized a 40-gallon tank to 50 pounds of pressure with just 33 strokes of the handle.  Any hand pump designed for water pressure for indoor plumbing, however, will work as demonstrated.