Quick Answer
To determine if your submersible pump is sized correctly, calculate the total dynamic head (TDH) of your water system, which includes the water level, pipe friction loss, and well casing friction loss. Compare this to the pump's maximum head rating. If the TDH is close to or exceeds the maximum head rating, the pump may not be sized correctly.
Calculating Total Dynamic Head (TDH)
Calculating TDH is crucial for sizing a submersible pump. TDH can be estimated by adding the following components: static water level (SWL), pipe friction loss, and well casing friction loss. For example, if the static water level is 100 feet, pipe friction loss is 20 feet, and well casing friction loss is 15 feet, the total dynamic head would be 135 feet. A submersible pump with a maximum head rating of 120 feet would be sufficient for this system.
Understanding Pump Sizing and Capacity
When sizing a submersible pump, it’s essential to consider both the pump’s capacity and head rating. A pump with a high capacity may not be effective if it’s not designed to handle the specific head requirements of the system. For instance, a 10 GPM pump with a maximum head rating of 100 feet may not be suitable for a system with a TDH of 120 feet. In this case, a higher-capacity pump or one with a higher head rating would be necessary.
Measuring Well Casing Friction Loss
Measuring well casing friction loss can be more complex than estimating pipe friction loss. This can be done using a well casing friction loss chart or by performing a site-specific analysis. For example, the well casing friction loss chart may indicate a loss of 10 feet per 10 feet of well casing for a specific pump type. If the well casing is 100 feet deep, the total friction loss would be 100 feet. This value should be added to the static water level and pipe friction loss to determine the total dynamic head.
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