Water Well Pump Replacement - What Size Well Pump Do I Need?

Determining the size of a replacement well pump.

Sizing a Well Pump Replacement

Installing the correct well components, properly sized for your water system is crucial for meeting your families needs today and into the future. The most important component of your entire well water system is your well pump. If your system is not performing, you may need a well pump replacement.

Let's examine some of the elements of your well pump and how to properly size it to meet your needs.

The Role of Your Well Pump In Your Water System

Well construction typically consists of three steps. First, a well is drilled on your property according to your local codes and standards. Next, a trench is dug from the well site to your home to connect the well to your home's plumbing. Finally, a pump is selected and installed to draw water from the well and deliver it to a storage tank placed in the home.

Selecting and sizing the well pump is the most critical step in the entire process. You need to make sure that the pump does not have a greater capacity than your well, but that is powerful enough to meet your needs. The pump consists of the pump itself and an electric motor. There are several different types of well pumps: shallow-well or deep-well, jet, and submersible. The type of pump you choose will be based on the physical properties of the well itself.

Well Pump Replacement: Determining Gallons Per Minute

The key to selecting the proper well pump is to figure out the the gallons per minute (GPM) you'll need during peak times in the household. You should select a pump that will meet the normal peak demand, rather than average use. There are two other methods for calculating use that should give similar results.

Residential Capacity Based on Fixture Count

The pump capacity in GPM should equal the number of fixtures in the home. Make sure to account for all water-using appliances in the kitchen, bath outdoor fixtures and special uses like a pool or hot tub. In this calculation, a home with two bathrooms (toilet, sink, and shower) kitchen sink, washing machine, dishwasher, laundry tub and two outside hose outlets would require 12 GPM based on 12 fixtures total.

Capacity Based on Peak Demand

A different model, using the same parameters as the previous example (12 fixtures) calculates capacity based on a seven-minute peak demand period. The typical peak use occurs in the morning as family members are preparing for the day, or in the evening when all are home. Seven minutes is the high water use time frame for a shower or automatic washer. There are charts available online that can help you to determine peak demand capacity using this method.

Well Pump Replacement for Addressing Low Well Capacity

In a proper well, the needs of the household are less than the rate that water can be drawn from the well. If peak demand exceeds this rate, the pump must be sized for the well capacity and peak demand is met through storage. Usually, a large storage tank can extend pump life as it reduces the need for cycling.

Most of the wear on a pump occurs when it starts and stops. Occasionally, if the well capacity is low, a two-pump system may be needed. The well pump supplies water to an atmospheric storage tank. A second shallow well pump delivers water from the atmospheric storage tank into the pressure tank in the home. Its operation is controlled using a pressure switch.

Ensuring Adequate Water Pressure

Water pressure is the final factor when determining pump size. Pressure must be sufficient to deliver water to the highest outlet and to operate modern appliances. For most appliances like dishwashers, this means a minimum 10 pounds per square inch (PSI). Lawn sprinklers typically require 20 PSI, sometimes up to 40. If you have a water treatment system, like a water softener, this can result in a pressure drop in the system and must be considered when determining required pressures.

If the pump is located far from the home, or at a lower elevation, higher pressure is required. A conservative method of determining proper pressure is to have a reading of at least 20 PSI at the fixture that is highest and farthest from the pump as measured when water is flowing through that fixture.

Well Pump Replacement: Selecting The Right Pump

Each type of pump has pros and cons. When working with your well water professional, review some of these factors before making a final choice.

• Adequate GPM for present, and future use
• Adequate pressure for present and future use (consider the possibility of a lower water level in the future)
• Cost
• Cost of installation
• Cost of additional materials like piping, fittings, accessories etc.
• Power supply
• The area needed for installation (is there adequate space available?)
• Reliability
• Cost and ease of servicing the pump
• Operating cost including power and parts.

If you'd like more information on your options when choosing a well pump replacement, contact the professionals at Skillings and Sons! (800) 441-6281