MIL-HDBK-1164
APPENDIX A (Continued)
Field Head Calculation
1. Assume that a pressure gage located on the discharge of a well pump indicates a
pressure of 35 pounds psi for a discharge of 500 gallons per minute (gpm). The
corresponding pumping level in the well is 60 ft below the elevation of the pressure
gage. The pump column is 8 inches in diameter and extends into the well 100 ft
below the pump discharge.
2. The friction loss for 500 gpm of water through an 8-inch pipe, with a friction
coefficient (C) of 100, is 8.1 ft divided by 1,000 ft. The equivalent length of an
8-inch long sweep elbow is 13 ft. Thus, the friction loss through the column and
discharge elbow can be calculated as follows:
8.1 ft
113 ft
= 0.9 ft
1,000 ft
For help with head loss calculations, refer to par. 2.1.1.
3. The vertical distance from the well pumping level to the pressure gage was given as
60 ft.
4. The pressure at the pressure gage expressed as ft of head equals:
2.31 ft
35 psi
= 80.9 ft
psi
5. Total field head is the sum of the friction loss, vertical distance, and pressure in ft of
head:
0.9 ft + 60 ft + 80.9 ft = 141.8 ft
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