How to Determine the Pump Size for a Deep Well

A deep well contains water that is at least 25 feet below the surface.
The right sized well pump will keep well water flowing efficiently.The right sized well pump will keep well water flowing efficiently.
To lift water from a deep well, the installation of a submersible pump is required. There is no benefit to buying a pump that is too large for the system, and in fact, it can end up more costly to do so. It is better to determine your water requirements and calculate the pump sized based on actual need.

Step 1

Find the well pipe diameter. Standard sizes are anywhere from 2 to 12 inches, with 4 to 6 inches being very common. This information should be on your home’s legal documents. You can also measure across the open top of the well.

Step 2

Count all fixtures in your home that use water. This includes tubs, showers, washing machines, dishwashers, sinks and any other fixtures you might have. If the well will be supplying water to a location other than your home, or in addition to your home, take those fixtures into account. Add them up and count each one as 1 gallon per minute of water requirement.

Step 3

Multiply the gallons per minute determined by the number of fixtures by 60. This is necessary because pumps are normally rated by gallons per hour, or GPH, rather than per minute. Multiplying by 60 converts GPM into GPH to help you choose the right pump.

Step 4

Determine the head rating you will require. This is the distance from the pump itself, when it is in place underwater, to ground level. This is how far the pump will have to move the water vertically, and is an important consideration when sizing a pump. The deeper the pump will be, the more powerful the motor must be. The head number is given as a range, so you don’t need to know the exact depth of the pump, although you should have a good idea. You can use a weighted line dropped down into the well to measure depth.

Step 5

Combine the three factors to select the right pump for your needs. P ump size is based on combination of the physical size, which is based on the diameter of the well, the GPH required, and the necessary head rating, or the vertical distance the pump must move the water.

Things You Will Need

  • Measuring tape
  • Weighted line


  • A deep well pump is often best installed by someone with experience, as there are factors, such as potential sand in the well, that need to be taken into consideration.


  • A pump that is too large for the system may draw water too fast, causing air to get into the system. Not only can this disrupt the smooth flow of water, it is also possible that it can cause the pump to burn out.