How Do I Replace a Deep Well Pump?


Deep well pumps spend their useful service life submerged under a hundred feet of water or more, pushing it to the surface for the needs non-municipal water users. They are constructed with the electrical part of the motor sealed and filled with propylene glycol at the factory to assure long life. Most pump manufacturers warrant their product for at least five years, and most pumps operating in clear-running wells may last from 15 to 25 years. Disassembly of an improperly functioning pump is strongly discouraged. If it becomes necessary for you to replace your deep well pump, however, here's how.

Pump Motors

  • Four-inch-diameter pumps intended for residential service move about 10 gallons of water per minute and maintain the water pressure tank in a band between 30 and 50 psi, which prevents the motor from overcycling. Pumps consist of a sealed capacitor start-type 230 volt AC single-phase motor with carbon sleeve water bearings, and a number of centrifugal pump stages to overcome 50 to 150 psi of static head due to the depth plus the flowing pressure requirements on the surface. The pump may be close to three feet long.

Removing Defective Pump

  • Shut off all electrical power to the well system at the main breaker box. Special lifting tools with a one-inch NPT end taps directly into the pitless adapter fitting about five feet down the well casing. Lifting this fitting off its mating slide starts the hoisting exercise to lift the pump from the well. Many have found that using a freewheeling spare auto tire positioned on a stand next to the casing to help round the flexible pipe smoothly to horizontal, and a lawn tractor to pull on the pipe, facilitates lifting the several hundred feet of water-filled pipe and the pump. Take care while lifting to prevent damage to the centering clips, pipe, power wires and motor drop safety rope. As the pump motor approaches the surface, it must be gently cleared around the pitless adapter slide in the side of the well casing. When it reaches the top, carefully lift it out and lay it on the ground. Inspect the system closely, including the entire pipe and all wires. Check the motor's connections and take electrical readings on the pump's leads per manufacturer's specs. Note any items needing replacement.

Replacing Pump

  • If the pump's inlet screens are clogged with sand and debris preventing water flow, there is a problem with the well itself that needs to be fixed before cleaning the screens and returning the pump to the bottom of the well. If the pump is not working, or it is not testing per electrical specifications, replace it. There is nothing a user can repair by disassembling the pump itself because it is sealed. Wires need very careful attention and new connections need to be heat-sealed with special deep well wire-splice kits. Returning the new system to the ground is the reverse of lifting it out, including taking care not to chafe the pipe or wires against the side of the well casing. The pitless adapter will have to be carefully aligned with the mating slide. Make sure there is no debris on the pitless adapter O-ring before reinstallation.

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