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Thread: sudden pressure drop below 30

  1. #1

    Default sudden pressure drop below 30

    Hi. I have a pump that run with the usual 30/50 settings. I have to put some air in the tank a couple of times a year and everything is fine.

    This week, the pump begin to kick in very low, below 10. I don't know why. I was thinking of the usual air in the tank problem.

    I've cheched air pressur ein the tank and put it as usual:28psi.

    But now the pump kicks in below 10 near zero and stop at 68.

    I've tried to ajust the control switch without succes.

    A weird thing happens when pressure goes off of the system, let's say after a flush. When looking to the meter, the pressure goes down slowly down to 30 psi and all of a sudden drops to 10 and less. So I can't adjust the control switch because I don't have my 20 psi gap between the kick in and tyhe kick out.

    Any idea?


  2. #2
    In the Trades Bob NH's Avatar
    Join Date
    Oct 2005
    New Hampshire


    If the gauges are correct then you probably have a pressure switch problem or the precharge exceeds the ON setting of the switch.

    It is also possible that the pipe to the pressure switch line is plugged and the switch is not responding fast enough. That would explain both the 68 psi shutoff with a 60 psi switch and the delay in turning on the pump when the pressure drops.

    Remove the switch and check the pipe and orifice if there is one in the switch. If in doubt, install a new switch.

    Following is a possible cause if the switch is known to be working.

    The pressure drops slowly as long as there is water in the tank. The water runs out of the tank when the pressure is equal to the precharge pressure.

    When the water runs out of the tank the pressure drops instantly to nearly zero and you "run out of water". That causes the pressure switch to operate.

    Here is a process that may help to verify and set the air pressure after you make sure the switch is working and if you still have the same symptoms (run out of water before the pump starts).

    1. Turn off the power to the pump.
    2. Run the tank out of water and shut off the drain when the pressure drops sharply. That is the signal that the tank is out of water.
    3. Run the pump for about 10 seconds to get some water in the tank, and shut off the power. The pressure on the pressure gauge (water side) should be the same as the air pressure in the tank.

    4. Using a scredriver or other tool, with the cover off the switch, lift the pressure plate away from the base of the switch until it snaps to the open position, as if it reached shutoff. If it won't stay in the OFF position then you DO NOT have TOO MUCH air in the tank. Don't go any farther in this list.

    5. Now, with the power still off, slowly vent air from the bladder to let the pressure on the air side drop until the pressure switch snaps to the ON position. This step makes sure there is still water in the tank when the pressure drops to the point where the switch actuates.

    6. Turn on the pump and see if the problem is solved.

  3. #3

    Default tomorrow

    Thanks a lot for this quick response, I have no time today but I'll do tests tomorrow with your advices.

    But I have another question about maybe the source of the problem. About 1 week ago, one of the faucets in the kitchen began to be hard to turn. I've noticed, by unscrewing the aerator (not sure of the englisj term) that there was a little rubber washer there that was broken, probably gone from the faucet.

    Could this be the source of a kind of leak and sudden malfunction of the pump?

    Thanks again.


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