Feet of head is typically measured in terms of vertical lift (the height above water level that you are pumping the water), but the diameter and length of pipe also has an effect on the performance of the pump. If you have a short run and use an adequate-sized pipe, the friction loss should be negligible compared to the “feet of head” but on longer runs friction loss must be considered.
Total Dynamic Head is the “feet of head” plus friction loss created by the pipe. To calculate the Total Dynamic Head, determine the height that the pump has to push the water above the surface of the pond that it is pumping from and add the friction loss (in feet of head) shown in the table below.
Example: If you wish to pump 70 gallons per minute (4,200 GPH) 10 feet above the pond water surface through 100 feet of 2” pipe, the table shows that you would need to add 7.76 feet of head, making it equivalent to pumping the water 17.76 feet high or 17.76 total feet of head. However, if you use 3” pipe instead, you would only need to add 1.13 feet of head, making it equivalent to pumping the water 11.13 feet high or 11.13 total feet of head. Clearly, using larger pipe allows your pump to move more water.
To determine friction loss for lengths other than 100 feet, simply multiply the figure by the fraction greater or less than 100 that you are using.
Example: If you are using 75 feet of pipe, multiply the figure that the table gives you by 0.75, or if you are using 125 feet of pipe, multiply by 1.25.
Friction Loss per 100 Feet of Plastic Pipe in Feet of Head
(Expressed as Gallons Per Minute vs. Pipe Size in inches)
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