Pump Selection

Discussion in 'Pumps and Tanks Well Forum & Blog' started by GPM, Apr 19, 2007.

  1. GPM

    GPM New Member

    Messages:
    5
    I have a Goulds 33GS pump with a Franklin 5 HP 3 phase motor that was installed in my well (static water at 240 ft, pump at 367 ft, 5000 gal pressure tank, on at 30 off at 50, want apx 35 gpm) with new 2" galvanized pipe and wiring in 1997. I was working near the well site one day recently and noticed that the pump kept running the entire 60 minutes that I was there even though I knew no irrigation was taking place.

    I removed the pipe from the pressure tank and installed a 2" tee with a pressure guage on one leg and a 2" ball valve on the other. I opened the ball valve and started the pump. Using a crude fill up 5 gallon buckets while checking my watch system i guestimate the flow out of the open pipe to be 25 - 30 gpm. When i closed the valve the pressure seemed to rise way to slow given the small volume of the pipe, and would not build over 50 psi. This pump is supposed to supply 37 gpm @ 50psi. So... I am thinking I have a pump problem.

    I can call up Grainger and get a similiar Dayton pump (according to the production chart at least) and Franklin motor delivered to my door on open account in 2-3 days for about 20% less than an identical replacement goulds unit that i have to send payment for, then wait 5-7 days, then drive 40 miles into town to pick up.

    Despite my whinning, the efficiency and long term reliability of the system is far more important than the small cost difference or the inconvenience involved in procurring the Goulds unit.

    What would the informed recommend?

    Thanks
  2. sammyhydro11

    sammyhydro11 Previous member

    Messages:
    709
    Location:
    Massachusetts
    I would suspect that maybe you have a break where water is being displaced before entering the tank or the motor is not coming up to speed. I have limited experience with 3 phase units but a good start would be by testing the amp draw on each leg.

    SAM
  3. valveman

    valveman Moderator Staff Member

    Messages:
    4,426
    Location:
    Lubbock, Texas
    Sammy is probably right about there being a hole in the pipe somewhere. With a 3 phase motor, it will also act that way is the motor is running backwards. Sometimes the electric company will reverse the phases for you up the line somewhere. If they have worked on the line, changed out a transformer, or anything else, they could have hooked it up backwards. I would try switching any two of the three wires going down the hole to the pump. This will make the pump run the other direction. The pressure will either be better or worse instantly. If it makes it better, the pump was running backwards. If it makes it worse, you probably have a hole in the pipe somewhere.

    The most common place for a hole in the pipe is at the bottom of the well, just above a brass check valve. This is caused by electrolysis from a connection of galv pipe to a brass or stainless check valve. You can stop the electrolysis by covering this connection with electric tape about 6" above the check valve. A hole in the pipe will usually cause air in the lines, or the pump to cycle on and off while no water is being used. No cycling, no air in the lines, pump is probably running backwards.
    Last edited: Apr 23, 2007
  4. speedbump

    speedbump Previous member

    Messages:
    4,540
    Location:
    Riverview, Fl.
    Another possible problem would be the pump running somehow without pumping water. This can produce enough heat to nuke an impeller or two. That would also show a reduced flow and pressure.

    Before going to Graingers, you might want to check my pricing.

    bob...
  5. GPM

    GPM New Member

    Messages:
    5
    a little more info

    Thanks for the input everyone.

    1) Is a leak in the down pipe is more likely than a worn out pump? Both were new when installed in Aug 1997.
    2) The amp draw while running varied from 16.1 to 16.9 per leg which is pretty close to what i got when the pump & motor were new - in 97 after the pump had run 10 minutes and the tank pressure was about 20 psi the legs were drawing 18.6, 18.9. 18.8. The next time the pump started they were all about 16.8.
    3) I am pretty sure all is well with the wiring as I have machine tools set up at the same service that are functioning normally, one of which is a hydraulic shear that would be the tattle tale - it will not operate if 2 wires are reversed.
    4) I've never noticed the pump cycling, however I have thought I heard the bubbling sounds of air coming into the tank long after the charge air should have been cleared from the pipe.
    5) Based on your experience, shoud I wait to purchase a new pump until I pull the existing one? The water is used to irrigate nursery trees as well as supply my house shop and office so I cannot be down for long.
  6. valveman

    valveman Moderator Staff Member

    Messages:
    4,426
    Location:
    Lubbock, Texas
    17.7 amps is service factor load on that 5 HP. Sounds like your pump is still pumping a full load. I still think you will find a hole in the drop pipe, just above the bottom check valve. If you don't let it run this way for too long, the pump should be OK. Fix the hole in the pipe and cover this connection with electric tape and it won't happen again.
  7. GPM

    GPM New Member

    Messages:
    5
    Followup

    In case anyone was wondering what I found to be the case.

    While pulling the sections of 2" galvanized drop pipe, we started seeing small areas that had corroded through and appeared to be seeping and a couple clear pinholes and were thinking that if you added them all up they could account for a substantial amount of loss.

    And then...below the static water level we encountered 1 length of pipe that had 2 splits each wide enough to slip a credit card through and apx 18" long. I can imagine how much water was recirculating as pressure at the surface got to be just under 50psi.

    I was surprised to see how bad of shape the pipe was in after only 10 years. We replaced all 357' of pipe and all seems to be back to normal.
  8. sammyhydro11

    sammyhydro11 Previous member

    Messages:
    709
    Location:
    Massachusetts
    Sounds like some pretty corrosive water. Glad to hear that you resolved the problem and we were able to help.

    SAM
  9. valveman

    valveman Moderator Staff Member

    Messages:
    4,426
    Location:
    Lubbock, Texas
    I was pretty sure it was a hole in the pipe but, I was not expecting to see pin holes and splits in the pipe all the way down. Galv pipe is all imported now and not as good as it used to be. You would need to check the pressure and weight rating but, I think you could hang this pump on Schedule 120 PVC pipe like Modern has, then you would never have to worry about corrosion again.
  10. Raucina

    Raucina Previous member

    Messages:
    515
    If guys here can hang a 100 pound pump on schedule 40 glued pipe at 800' then its a pretty sure thing the 120 plastic pipe will hold.

    Fortunately, I believe there is some schedule 80 pipe and many ductile fittings still made here in the usa. And believe it or not, at least 3 large steel mills are presently under construction here- One, US owned, one Russian, and one Indian. weird world.
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