How a Shallow Water Pump Works

A shallow water pump relies on atmospheric pressure to work. Each time the operator pumps the handle, a piston moves up and down inside a cylinder that extends by a shaft or pipe into the well water. The piston creates suction by reducing the pressure above the water in the shaft.

When the pump is not in use, water in the well is subject to whatever the natural atmospheric pressure happens to be at that time in that location. In this condition, the water level in the shaft or pipe that extends into the well is the same as the rest of the water in the well surrounding the shaft.

The level of the water in the pump's shaft---just as the level of the water in the rest of the well---is a function of the air pressure immediately above it. When that pressure decreases, the water level rises. Pumping the handle operates the piston, and the piston---as it travels up and down in the shaft---creates a partial vacuum or suction that reduces the pressure above the water surface inside the shaft.

The water surrounding the shaft is still subject to full atmospheric pressure. However, since the water inside the shaft has reduced pressure above it, the surrounding water in the well---being pressed down upon by the atmosphere---exposes the water inside the pump shaft to more pressure from below than above. The net result is that the water level inside the pump shaft continues to rise as long as someone operates the pump. Once the pressure in the shaft is low enough, the water rises and begins flowing out the spigot.

It's a simple law of the physics of our atmosphere that we cannot pump water by means of a manual shallow well pump like this to a height of more than about 25 feet. This is because atmospheric pressure is the force that causes the water to rise inside the pump shaft, and atmospheric pressure is limited. Theoretically, with a perfect vacuum at sea level, the limit is around 33 feet. However, since that perfect vacuum inside the pump is extremely difficult if not impossible to achieve, the real limit is much lower. Also, the higher the elevation above sea level, the lower the maximum pumping height.