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Thread: Pump won't reach cutoff pressure

  1. #1

    Default Pump won't reach cutoff pressure

    I'm glad I found this forum. I have a problem I can't seem to figure out. We have an old remodeled farmhouse with an old well. I don't really have many problems with it except if you run water to long sometimes it will lose its prime. It has been a dry summer so far and last wekend I used a pressure washer. When I noticed the water starting to spit I stopped using it. Now 3 days later the pump runs and will only get to 30 pounds of pressure on the guage never reaching the cutoff pressure, which is 40. I have to unplug it to stop it from running. Would this happen if the well water is low? The pressure switch setting are 20 / 40. Any ideas or advise will be appreciated.

    Mark

  2. #2
    DIY Senior Member Hube's Avatar
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    It may be that there is some blockage (crud) ator near the pressure switch. It may need cleaning. Turn off the pump's power, and check this pipe (tube) out.
    Post back with results, and if needed, we can advise further.

  3. #3
    That's all folks! Gary Slusser's Avatar
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    IMO you had a dry well condition, or a leak in the plumbing going down the well. The loss of prime proves that. If you allowed the pump to run very long (5+ minutes) in that condition, it probably caused damage to the pump impellor, seals etc..

    Gary
    Quality Water Associates

  4. #4

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    I removed the tube and blew it out with compressed air. There was some crude when I first took it off. After putting it back on the pump ran up close to 40 pounds but didn't seem to want to cut off so I adjusted the cut off pressure to 38 and it seems to be working fine now. Thanks for the great advise. I really appreciate it.

    Mark

  5. #5
    That's all folks! Gary Slusser's Avatar
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    If the tube was blocked the pump wouldn't (have) come on when it should, and then it wouldn't shut off when it should; 20/40. Cleaning the tube would stop that but your problem is that the pump isn't building over 38 psi of pressure; proven by your need to decrease the cut out pressure setting to 38 to get it to shut off. Adjusting the switch proves that the switch sees the pressure and that the pump can't build more pressure, so you still have a worn pump or leak etc.. Expect it to not be capable of reaching 38 sooner than later.

    Gary
    Quality Water Associates

  6. #6

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    I think you're right Gary. It worked fine for a couple of days after cleaning out the line. Now it runs but won't reach the cutoff pressure again. I'm not sure if it's the pump or a possible leak. It seemed to hold the pressure when it did reach the cutoff, so I don't think it leaking, but not really sure. The pump did run for a while when it lost its prime too. I am still convinced the water level is low. It started acting up after doing a few loads of laundry. Any more ideas? Would it make sense to replace the pump and if so should the tank be replaced or just the pump?

  7. #7
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    You didn't mention if this is a shallow well pump, centrifugal or deep well.

    Is the pump offset from the well or on it
    Do you have two pipes leaving the pump to the well or just one?
    This is a well isn't it???

    bob...

  8. #8

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    It is an old well with a shallow well pump and 1/2 HP motor. There is only one pipe leaving the pump to the well. Also I read other posts and keep seeing about adjusting air pressure in the tank, I have looked at the tank and don't see any where to this. Are there tanks that don't use the bladder?

  9. #9
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    The tank will have nothing to do with the pump shutting off or not.

    If you want to know how to set a tank up, I can copy a Q/A from my website and paste it here. I don't know if I can advertise here or not.

    Your water level has obviously dropped enough to keep the pump from making 40 psi. When it comes back up, the pump will do the same if you readjust the switch. Or you can get a better (bigger) pump that will do more pressure. Not all pumps are created equal. Some will only make 40 top end, some will do 70. hopefully the water level don't get to 25' or less. Then it won't pump at all.

    bob...

  10. #10
    Retired Defense Industry Engineer jadnashua's Avatar
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    Most modern pressure tanks use a bladder. There are some designed as air-over-water. Basically, you start out with the tank drained. The pump starts to fill the tank up, compressing the air (it is trapped by the design by where the input output lines are located I think). Before the tank is full, the compressed air pressure causes the tank to reach the cutoff point for the pump controller. The disadvantage of this type of system, is there is nothing to separate the air from the water, and eventually, air is absorbed by the water flowing through the system, and then you need to recharge it.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  11. #11

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    Since this is a shallow well pump, it's possible that the nozzle is plugged up. This will keep the pump from building pressure.
    Ron

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