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Pueblo
101 Spring Street 81003
719 542 5631
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Pump Sizing and Selection
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There is some basic information that is necessary for sizing of a water pump system. Most pump sizing will be based on Total Dynamic Head (TDH). This is the total pressure or head a pump must develop. The information necessary for determining the TDH is as follows:
SERVICE PRESSURE
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The range of pressure the pressure switch will be set at for the pumping cycle.
ELEVATION/VERTICAL LIFT
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The vertical distance between the well head and the point of use.
PUMPING LEVEL
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The lowest water level reached in the well during the pumping operation. This is the static water level (standing water level before pumping) and the draw down (the distance the water level is lowered during pumping) to determine the total lift from pumping level to the well head.
HORIZONTAL RUN
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The horizontal distance from the point the water enters the piping at the well head to the most remote point of use.
FRICTION LOSS
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The loss of pressure or head due to the resistance to flow in the pipe and fittings.
THE GALLONS PER MINUTE DESIRED AT THE POINT OF USE
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The maximum gallons per minute required at the point of use. This will be limited by the production of the well and code compliance at the well location.
WELL SIZE
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The inside diameter of the well in inches.
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Determining Total Dynamic Head
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Take the pump switch shut off pressure multiplied by 2.31 to calculate the head in feet required. Example with a 30/50 pressure switch, take the cut-out pressure 50 x 2.31 = 115.5 feet of head.
Next take the vertical lift in feet. For this example we will use fifty feet = 50 feet of head.
Next is the pumping level in feet. Let's use seventy five and a half feet for this example = 75.5 feet of head.
Consider next the friction loss through the piping. This is the total length of vertical and horizontal piping, the number of fittings to the most remote outlet and the piping material (copper, plastic, steel). Also the desired gallons per minute of flow rate is applied here for use with the friction loss charts. For this example we will use a flow of ten gallons per minute through two hundred fifty feet of one inch plastic pipe with four elbows. Using the plastic pipe chart and fitting chart from the links below the friction loss will be:
10 gpm through 1"pipe = 6.88 feet of head per 100ft (from Chart)=
6.88 x 2.5 (250 Feet of Pipe)=17.20 Feet of Head
One inch 90 from chart = 2.7 feet of head x four = 10.8 feet of head
Total Friction Loss head 17.2 +10.8 =28 feet of head.
Add all the calculations in red above to find Total Dynamic Head. In our example this total is 269 feet of head.
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Take the Total Dynamic Head calculated by the method above and then use the pump curve charts from your pump manufacturer to select the proper pump. The link below shows the pump we would select with our RED JACKET submersible pump line. From the chart at 269 feet of dynamic head the 1 HP 12S14 pump would deliver 11gpm.
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Pump Sizing and Selection are as easy as ABC. Gather the information in the first section above then contact us and we will calculate the Total Dynamic Head for you and suggest the pump for your application.
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