Lawn Sprinkler Pump Short Cycle

Discussion in 'Irrigation / Sprinkler Forum' started by johnc3640, Jul 20, 2010.

  1. johnc3640

    johnc3640 New Member

    Messages:
    1
    Location:
    Michigan
    I just recently replaced my old 1.5 HP Sta Rite lawn sprinkling pump with a new Wayne 2 HP lawn pump. The old pump was controlled by a pressure switch (no pressure tank) and worked fine. The new pump, with the same pressure switch, short cycles continously, even with all zones closed. Because the new pump is bigger, and likely more efficient, does this mean I now need a pressure tank? How do you determine what size?
  2. zl700

    zl700 DIY Senior Member

    Messages:
    237
    Location:
    Texas
    Bigger is not always better.
    Your old pump was sized properly to deliver the required GPM and pressure within the operating parameters of the irrigation system requirements. You new pump produces higher pressures and GPM volume thus, it is able to reach shutoff point of the pressure switch. This cycling will kill you in energy costs starting the motor so many times, besides wear it out quickly.

    A tank may help but will most likely just slow down the frequency of cycles. Many things can be done such as trim the impeller, add more zone demand to increase flow requirements, install or use a balance valve to decrease flow at pump outlet/inlet or a combination of all these that would work best.
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