How Do You Size A Submersible Well Pump?

Introduction

A submersible well pump is an essential component in every well system. It plays a vital role in the water extraction process, making it possible to pump water from deep underground. However, buying a submersible well pump can be overwhelming, especially for beginners. One of the most challenging aspects is sizing the pump to fit the well casing and the water needs of the household. In this article, we will discuss how to size a submersible well pump and provide some helpful tips.

What is a submersible well pump?

A submersible well pump is a type of pump that is designed to be placed underwater. It is connected to the water supply line and is located deep underground, often hundreds of feet below the surface. The pump uses an impeller to draw water from the well and push it to the surface, where it can be used for various purposes, such as irrigation, domestic water supply, or commercial purposes.

Why is sizing a submersible well pump important?

Sizing a submersible well pump is essential because it determines the amount of water that can be extracted from the well. If the pump is too small, it won''t be able to supply enough water to meet the household''s needs. On the other hand, if the pump is too large, it will be more expensive to operate and maintain, and it may not be efficient in pumping water from the well.

Factors to consider when sizing a submersible well pump

The following are the critical factors to consider when sizing a submersible well pump:

1. Well Depth: The depth of the well is a crucial factor in determining the pump''s size. The deeper the well, the more power the pump requires to push water to the surface. It''s essential to ensure that the pump has enough head pressure to get the water to the surface.

2. Well Casing Size: The well casing is the pipe that lines the borehole. Its size can affect the pump''s size, as smaller casing sizes may limit the pump''s size that can be installed. It''s crucial to know the well casing size to ensure that the pump can fit and function correctly.

3. Water Demand: The amount of water needed to supply the household is also a critical factor in sizing a submersible well pump. It''s important to consider the number of people living in the house, the number of bathrooms, appliances that use water, and the daily water use to select the appropriate pump size.

4. Water Quality: The quality of water in the well can affect the pump''s size, as certain minerals, bacteria, or sediment can clog the pump or reduce its efficiency. If the water quality is poor, a larger pump may be required to compensate for any blockages.

5. Pump Efficiency: The pump''s efficiency determines how much energy it requires to pump water from the well. Selecting a highly efficient pump can save energy costs in the long run by using less power to pump the same amount of water.

Steps to size a submersible well pump

The following are the standard steps to size a submersible well pump:

Step 1: Calculate the Peak Demand Flow Rate

The peak demand flow rate is the maximum amount of water needed during the busiest times in a household, such as when showers, washing machines, and dishwasher are running. It''s calculated based on the following parameters:

1. Number of bathrooms
2. Number of people living in the house
3. Appliances that use water, such as washing machines, dishwasher, and irrigation systems.

The average peak demand flow rate for a household of four is around ten gallons per minute (GPM). However, this rate can vary depending on the water demand of the household.

Step 2: Calculate the Total Dynamic Head (TDH)

The Total Dynamic Head (TDH) is the total amount of head pressure required to lift water to the surface from the well. It''s calculated based on the following parameters:

1. Depth of the well
2. Distance from the water surface to the pump intake
3. Friction loss due to the diameter and length of the pipe.

To calculate the TDH, you can use the following formula:

TDH = Static Head + Friction Loss + Intake Head

Static Head = Depth of the Well + Height of the Tank if Above the Pump

Friction Loss = (Pressure Drop due to Pipe Diameter) + (Pressure Drop due to Length of Pipe)

Intake Head = Distance from the Water Surface to the Pump Intake

Step 3: Select the Appropriate Pump Size

Once you have calculated the Peak Demand Flow Rate and Total Dynamic Head, you can select the appropriate pump size from the manufacturer''s sizing chart. You can match the flow rate and TDH value to the pump curves to identify the right pump size and model.

Tips for sizing a submersible well pump

1. Make sure to measure the well casing diameter before selecting a pump size.

2. Take into account the water use habits of the household when calculating the Peak Demand Flow Rate.

3. Ensure that the pump''s total dynamic head is sufficient to push water to the surface and meet the household''s water needs.

4. Consider water quality when sizing a pump, as poor water quality can clog or damage the pump.

5. Choose a highly efficient pump to save energy costs over time.

Conclusion

Sizing a submersible well pump is critical to ensuring that the water supply is adequate and meets the household''s needs. It''s essential to consider several factors, including well depth, well casing size, water demand, water quality, and pump efficiency. By following the steps outlined in this article, you can confidently select the appropriate pump size and model for your well system.