The average life expectancy is 10 to 15 years for a residential 3-wire and 8 to 13 years for a residential 2-wire well pump. Life expectancy of the pump depends on many different factors, some of which are the quality of the pump, how often the pump has to run, and the electrical supply to the pump. Here is a list of some of the factors that determine life expectancy.
- Avoid upthrust and downthrust. When there is lower pressure (low head) the impellers will “float” up and wear on the diffusers above. In an upthrust position there is a higher volume of water being pumped against lower pressure. When there is more pressure pushing down (high head) the impellers will “float” down and wear on the diffusers below. In a down thrust position there is a lower volume of water being pumped against higher pressure. A pump is running within it’s recommended operating range the impellers will float between diffusers, thus reducing wear on the pump. This will occur when the pressure pushing down from above and the flow of water coming from below create a balance. The balance of pressure and flow when running in the pumps designed sweet spot will limit wear and, therefore, extend the life of your pump.
- 2 vs 3-wire: A 3-wire motor requires a control box to be installed for the pump to operate, whereas a 2-wire will have all the necessary starting components inside the pump’s motor. The benefit to having a 3-wire motor is that if the pump fails to start, you can begin your electric troubleshooting at the control box. If something in the box failed, simply replace it and you’re up and running. With a 2-wire motor you do not have this luxury. If you want to test or replace anything you will have to pull it out of the ground. This subtle difference usually ends up giving 3-wire motors about 2 more years of service life than 2-wire motors.
- Duty Cycle: A pump which is called-on to run just a few times a day will have a considerably longer life than the same pump under heavy or continuous use. One of the reasons that owners install a larger water pressure tank is to extend the water drawdown cycle and thus reduce the frequency of turning the water pump on and off. A properly sized pressure tank will also ensure that the motor runs for a minimum of one minute to dissipate heat build up from starting current. If your pump is cycling 50+ times a day I would expect less than 10 years from it.
- Motor Quality: The quality of the motor will affect how long the pump will last. Variables include the type and quality of electric motor bearings and its lubrication requirements. Franklin Electric, the company that invented submersible motors, are the most durable and rugged motors out there. I would expect a low quality motor to last half as long as a high quality one.
- Sediment: Sand and abrasives are a major wear factor on the pump assembly itself (as opposed to the electric motor that drives the pump). Sediment in water acts as an abrasive that wears pump bearings and other moving parts. We’ve seen pumps last less than 2 years because of extreme sediment buildup, and others last 15+ years when no sediment is present.
- System Installation: The quality of the well water system installation can make a big difference in the life of the equipment. Installers who simply hook up a pump and wiring, with no understanding of the importance of proper location of check valves, filters, proper electrical wiring, etc. are likely to provide a shorter-lived water supply system.
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