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How to size the mill to your well... |
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| The first step in purchasing a windmill to pump water from a well is to have the well drilled. Once the well is drilled, you need to get two vital pieces of information from your driller: the total depth of the well and the static water level. These 2 items are needed to correctly size the windmill to your water well. In addition to the well depth and static water level, you also need to know how far above the top of the well you will need the water be discharged. | ||||||||
EXAMPLE
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Using the information in the example, look at the following chart: |
| Table of Pumping Capacities | ||
| This chart if for a 1-7/8" cylinder | ||
| Pumping Capacity: 3 gallons per minute (GPM)* | ||
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Wheel Diameter |
Pumping Elevation (in feet) |
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| Long Stroke | Short Stroke | |
| 8 Foot | 175 | 233 |
| 10 Foot | 260 | 346 |
| 12 Foot | 390 | 519 |
| 14 Foot | 560 | 745 |
| 16 Foot | 920 | 1224 |
| * In a 18 to 20 Mile Per Hour (MPH) wind |
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The proper windmill head diameter for the example is an 8' head. This assumes you will use
the standard long-stroke of the windmill. If you use the short-stroke your water production
decreases by 25% and pumping elevation increases by 33%.
Optimum tower height is determined by the location of the windmill with respect to the surrounding structures. To obtain the optimum performance from your windmill, it should be located 400 feet from the nearest structure and the top of the tower should be 15 feet taller than the tallest surrounding structure. This is if we lived in a perfect world. Sometimes the well must be drilled in a less than optimum location. Then, you just get the tallest tower your pocket book can afford to clear the top of the nearest sturcture(s) in the path of the prevailing wind. Lets add to our example. We know we have 160 feet of lift and lets say you have a single story house to the north of the water well and a small barn/workshop that is on the south side of the water well. Lets also assume that the wind is normally from either the south or the north. Lets say that the top of the tallest structure is 18 feet tall. Using this information the shortest tower that should be used is a 33 foot tower. A water pumping windmill will produce a minimum of 3 gallons per minute (gpm) in a 18 to 20 MPH wind. This is assuming that the pump (working barrel) in the bottom of the well is a 1-7/8" diameter cylinder that is connected to 2" drop pipe. You can get a greater production of water if you use a larger cylinder and larger pipe. You will also need a larger windmill head to lift the larger amount of water. Your need for more water will come at a greater initial expense. You can also use a closed top cylinder (which connects to pipe smaller than the diameter of the cylinder) but remember, when the time comes to change the leathers on the valves in the cylinder, with a closed top cylinder, you have to pull the rod AND the pipe at the same time. With an open top cylinder, you only need to pull the rod. Let the depth of your well determine the type of cylinder you will use. If all this is confusing, after you get your well drilled, give me a call and I will help you. |