Aermotor Windmill Texas 2010

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How a Windmill Works - Cylinder Pumps

Cylinder Pump

The cylinder pump is located inside the windmill's drop pipe near the bottom of the water well. It pumps water from the bottom of the well by ratcheting it upward through the drop pipe, towards the storage tank.

It achieves this by repeatedly drawing water in through the bottom of the drop pipe and lifting the water column upward. This cycle repeats until water pours out of the top of the drop pipe into the storage tank.

Cylinder Pump Valves

Two valves work together in an opposing manner to pump water. The top valve is called the "plunger" and the lower valve is called the "check valve". Power is provided by the windmill motor and transmitted to the plunger through the sucker rod.

Several Things Happen At Once ...

As you view the animated cylinder pump illustration keep several things in mind:
  1. Water can only flow upward through the valves. It's strictly an upward, one-way flow of water.
  2. Each valve has a watertight seal at its base. Water passes through the valve's bottom then up-and-out through the valve's side vents.
  3. When a valve's ball is down, the valve is closed. When a valve's ball is up, the valve is open.
  4. Only the plunger moves. The plunger's seal is watertight in the drop pipe. But as it slides up and down, the plunger creates a pumping action.
  5. The lower check valve is fixed in position. Water enters through the strainer and flows upward through the check valve.
  6. When the wind stops blowing, both valves close and pumping stops, The water column above the plunger and the "cylinder water" trapped between the two valves are held in place, ready for the pumping to resume when the wind begins to blow again.
. . . . .

Ball Valves in Action

The ball's orientation in the valve basket is the key.

• When the ball is "up", the valve is open.
• When the ball is "down", the valve is closed.

Water Flows Upward

Dark blue well water is drawn upward through the lower check valve, filling the cylinder pump.

The sky blue water column water above the plunger is lifted upward.

Pale blue water in the cylinder area becomes the new bottom of the water column as the plunger moves downward.

Valves Work in Opposition to Each Other

When the wind blows, the plunger moves up and down. As the plunger moves, each valve opens and closes at the appropriate time causing water to be pumped upward.


On the upstroke, plunger valve closes and the check valve opens. Water above the plunger (the water column) is lifted. This lifting motion also creates a vacuum between the plunger and the check valve. This vacuum opens the check valve, and well water flows up through the strainer into the drop pipe.


On the downstroke, plunger valve opens and the check valve closes. The plunger can then pass through the water being held "in check" by the lower check valve. This downstroke forms the new bottom of the water column.

View the animated windmill illustration to see everything in action.