To avoid turbulence caused by surrounding objects, the blades of water-pumping windmills should be at least 30 feet above any obstructions such as trees or buildings in a 300-foot radius. Access to “clean wind” helps the windmill operate smoothly, ensures a more effective operation, and extends its life. This often means installing a tall tower, so you can get well above nearby buildings, trees, and land features.
Although you can select and site a windmill without using local wind-speed data, correctly sizing the windmill and pump cylinder (see How Much Will it Pump?) using real data will remove much of the guesswork about how much the ‘mill will pump. A well-selected and well-sited windmill should start pumping water at wind speeds between 6 and 8 mph. Most windmill manufacturers rate a windmill’s pumping capacity for winds in the 10 to 20 mph range. You should be practical—don’t size the windmill at its peak pumping capacity, or as if it’s only going to experience high winds.