Jet pump won't build cut off pressure

Discussion in 'Pumps and Wells' started by harpaholic, Sep 5, 2015.

Help Support Plumbing Forums by donating:

  1. Sep 5, 2015 #1

    harpaholic

    harpaholic

    harpaholic

    New Member

    Joined:
    Sep 5, 2015
    Messages:
    2
    Likes Received:
    0
    Location:
    ,
    Hi,

    I had a 1/2 hp convertable jet pump at my cabin for 18 yrs. I have a shallow well with a max depth of 10ft from ground to bottom of well. Pump is in my camp about 4ft above ground level. Recently my pump would kept running and would not shut off unless I cut the power to it. Never had an issue with the system before. I changed the pressure switch which was 20/40 to a 30/50. (the only one I could buy) I readjusted my pressure tank up to 28 lbs when empty. Pump would still keep running so I took the end off of my the pump and made sure the nozzle and venturi were clean. This also made no difference. I decided the pump must be at fault so I replaced the pump with a new 1/2 hp shallow well jet pump. Now I can still only get pressure to build to 43lbs. I have replaced the foot valve on my "older" 1" underground PVC waterline with a new 1" one. This line has a pitless adapter on it at the well. Still no difference. I purchased a new 1" PVC line and new foot valve which I just dropped into my well. Still no difference in the amount of pressure. My old pump had a 1" inlet on it, my new pump has an 1 1/4" inlet on it which I have reduced down with a metal bushing to accept a 1" waterline and it has a 1" outlet. All of the plumbing guys who I know that does this work for a living tell me that's acceptable and should not affect the operation of the pump.

    It is a single line from the pump to the pitlass adapter/well, a distance of about 60ft. I have replaced the seal on the adapter. Once I cut power and read my pressure gauge, the pressure holds which tells me there is no leak in the system. I can shut off the main line in my cabin about 10ft away from the pump and there is no leaks from the pump to there either. Also as I mentioned I have tried it with a brand new suction line with same result.

    Here is a link with the specs of the new pump. Its called a Little Giant. 1/2 hp wired for 115v http://littlegiant.com/media/130632/995259.pdf​

    My old pump is a GSW CJC50 313501(313 series)(501 1/2 hp)



    Why does my pump not reach cutoff pressure?
     
  2. Sep 6, 2015 #2

    speedbump

    speedbump

    speedbump

    Wells & pumps; not a... Professional

    Joined:
    Jan 6, 2010
    Messages:
    1,723
    Likes Received:
    212
    Location:
    Riverview, Florida
    60' of suction line running horizontally being 1" is a friction loss, the depth to water in the well may have dropped a little and your only dealing with a half horse pump. A good quality 1/2hp jet pump will make anywhere between 40 psi and 50 psi if all is well. Start adding suction friction loss and low water levels and the shut off pressure will drop. You have already fixed everything that would have any effect on the system. So either buy a bigger pump, change the venturi in your existing pump to a smaller one or get used to what you have. There really isn't much else you can do.

    Your link is broke, but I looked up a 1/2hp little giant jet pump and the literature says it can make 60 psi max. That is of coarse if everything is perfect.
     
  3. Sep 6, 2015 #3

    Matt30

    Matt30

    Matt30

    Professional Professional

    Joined:
    Jan 17, 2012
    Messages:
    2,142
    Likes Received:
    826
    Location:
    Halifax, Nova Scotia
    18 years of well dirt and sediment and god knows what else, that pump just ain't as strong as it used to be. Have it taken apart and cleaned, or replace. They don't last forever!
     
  4. Sep 7, 2015 #4

    harpaholic

    harpaholic

    harpaholic

    New Member

    Joined:
    Sep 5, 2015
    Messages:
    2
    Likes Received:
    0
    Location:
    ,
    Hi,

    Went back to camp yesterday.

    Dug up both ends of my underground line. Found a "considerable" leak next to the outside of the well where the line went on the pitlass adapter. Repaired the leak. Could find no other leaks. Took off all of the fitting on the pitlass and drop pipe, retaped and tightened them. Heated the pipe with a torch before we clamped them so as to make a good seal. 6ft of water in well.
    Pump could still only make 43lbs of pressure, fixing the leak made absolutely no difference in the amount of pressure it made.
    Have decided that the pump or system as it stands is never going to make 50lbs of pressure. Adjusted cut off to 40lbs and expansion tank pressure to 18lbs. Pump cycles as it should. However why this system cannot generate 50lbs of pressure is beyond me.

    Speedbump I think you are correct and have hit the nail on the head!!!


    Thank you very much to all of you who provided advise!!!
     

Share This Page