Sizing Your Submersible Well Pump Correctly

Sizing your submersible well pump correctly

How to determine according to your system, what pump size is needed?

Two values- flow rate and lift amount need to be calculated for doing the pump sizing properly.

·         Flow rate: In a particular time, the water volume that passes through the pump in GPM (gallons per minute) is the flow rate

·         Lift: It is also called the total dynamic head. It is the amount of lift that is needed.

Estimating the flow rate

Desired flow rate can be calculated through several methods. If you can figure out the water consumption at peak time in GPM, you can size your pump accurately. Among the various techniques to determine flow, I will discuss the Water Systems Council's one.

Water systems council uses the water usage in gallons in the seven minutes when the demand is on peak for calculating flow rate in residential areas. For example, for homes with 3-4 bathroom flow is considered 17GPM, whereas, for a one bathroom room home, it is set as 7 GPM. Regardless of the method used in calculating flow rate, once you know it, ensures your well can endure it.

Calculating Total Dynamic Head (TDH):

A.      Vertical lift: The distance between the pressure tank’s top and the pitless adapter

B.      Service pressure: Multiply the average setting of your pressure switch with 2.31

C.      Pumping level: The distance from pitless adapter/well seal to the water drawn level on which the flow rate is dependent.

D.     Frictional loss: According to flow rate, kind, and length of piping and its fittings, there will be a loss at the head when the water is passing through the pipe. To make this calculation, you would need a calculator or table for friction loss.

To calculate the total dynamic head add all the four values above.

Total dynamic head= A+B+C+D

Once the total dynamic head and flow rate is calculated, you can pick the appropriate pump.