Well pump chattering on shut off

Discussion in 'Pumps and Tanks Well Forum & Blog' started by JimmyG, Aug 7, 2014.

  1. JimmyG

    JimmyG New Member

    Messages:
    9
    Location:
    Florida
    Hi folks,
    I have a submersible well pump that recently started chattering when it gets to pressure. After reading other post I thought it was the pressure switch contacts chattering. I could not see the contacts chattering but could here it. I used a piece plastic to manually open the contacts to be sure they were not bouncing. They are not but it sounds like the pump is quickly turning on and off several times when it gets to pressure. Nothing has changed in the plumbing setup in years. Any help would be appreciated.
  2. Reach4

    Reach4 Well-Known Member

    Messages:
    2,642
    Location:
    IL
    Your pressure switch should be connected very close to the input pressure tank. Presuming that is the case, and if the pump runs for about a minute or more before reaching shut-off pressure, then I expect your pressure switch is bad. They are fairly inexpensive.

    If the pump runs for a much shorter time, that might indicate a different problem.
  3. DonL

    DonL Jack of all trades Master of one

    Messages:
    4,443
    Location:
    Houston, TX
    You should check your water tank. It may be waterlogged, or the air pressure may not be correct.

    Water is hard to compress, and the switch don't like it. Not great for the pump either.


    Just a guess from miles away.
    Last edited: Aug 7, 2014
  4. JimmyG

    JimmyG New Member

    Messages:
    9
    Location:
    Florida
    The pressure switch is 12 inches from the pressure tank. It only takes about 20-30 seconds to pressurize to 60 psi. When the pump stops there is a hammering noise, and I can see the pressure jump around. This only last 1-2 seconds.
  5. JimmyG

    JimmyG New Member

    Messages:
    9
    Location:
    Florida
    I checked the pressure tank by draining the tank then checking the air pressure. It was a little low at 32 psi, I filled it to 38 psi.
  6. Reach4

    Reach4 Well-Known Member

    Messages:
    2,642
    Location:
    IL
    Your pressure tank may be going bad. The failure mode would be that the bladder/diaphram has a leak, and water has replaced part of the air. What I don't know is how that translates into the pressure fluctuation large enough to make the pressure switch twitch.

    When your pump runs and shuts off, there should be a usable drawdown of water available of about 25% of the nominal tank capacity. So about a 44 gallon tamk should be able to let you draw about 11 gallons. A 10 gallon per minute pump would take a little over a minute to fill that tank when no power is being used. So when the pump shuts off, and no water is being used, turn off the pump. Put water from a tap into a bucket or other container, and measure the total water that you can draw. If it is close to what you expect, your pressure tank is OK. If it is much less, the tank needs replacing or in a few cases some can be repaired.

    So if the pressure tank proves OK, replace the pressure switch. If is drawdown substantially low, then I don't know if that would totally explain your symptoms or not. Others with experience will probably have good information for you after hearing the results of your drawdown test.

    You should also identify some other things if you know them. What is your pump model (GPM and HP), how deep the well is, and how far down the water surface is.
  7. valveman

    valveman Moderator Staff Member

    Messages:
    4,549
    Location:
    Lubbock, Texas
    It sounds like your check valve is sticking and will finally close after a couple of bounces.
  8. DonL

    DonL Jack of all trades Master of one

    Messages:
    4,443
    Location:
    Houston, TX
    20 -30 second run time, sounds a bit fishy to me, What size tank do you have ? A cycle stop valve may be in order.

    What is your on/off pressure difference ? Have you tweaked it ?

    You may have more than one problem. Valveman may have hit the nail on the head on the bounce problem.
    Last edited: Aug 8, 2014
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