how to replace a submerged well pump

Discussion in 'Pumps and Tanks Well Forum & Blog' started by Kendallroad, Mar 5, 2008.

  1. Kendallroad

    Kendallroad New Member

    Messages:
    14
    I would like to replace my 1/2 hp well pump with either a 3/4 hp or a 1 hp pump in 325 ft deep well tested 10 years ago at a capacity of 20 gpm.

    Is this a do-it-yourself,(with help from friends)?

    The local well driller wants $1800 to $2000 for the replacement.

    I believe that I can the pump at cost iabout $500 to $700 depending on make and hp.

    Any thoubhts on this project?

    Kendallroad
  2. valveman

    valveman Moderator Staff Member

    Messages:
    4,383
    Location:
    Lubbock, Texas
    325' is pretty deep. If it is hanging on PVC or Poly pipe, and it is not stuck, you and a couple of friends can probably pull it out. If it is steel pipe, it's gonna be REAL heavy. If you can lift it, anyone can pull and set a pump. However, it is the little stuff that makes a pump man worth while. Knowing how to get a pump unstuck, how to splice the wires, how to attach the wire to the drop pipe, knowing that you can't attach a steel fitting to a brass or stainless one without insulation, and simply knowing something isn't right when he sees it, makes a pump man worth his salt.

    If all goes well you can save yourself a little money. If you drop that pump in the well, $2,000 for a pump man would have been cheap. Even charging $2,000, you won't see very many rich pump guys. We learn this stuff the hard way by having to spend 3 or 4,000 bucks to fix your $2,000 job when something doesn't go right. Some pump guys have some old rigs that are paid for but, most have to make payments on rigs that cost from $50,000 to $250,000. Then there is the insurance payments, fuel, tools, license fees, phone bills, advertisements. Then if your employees show up, you have to pay them as well. Something goes wrong under warranty, and there is another trip without compensation.

    It usually gives people a good appreciation for a pump man when they pull a 325' well themselves. Everybody should try it once, then the price quoted by a pump man doesn't seem nearly as high.
  3. speedbump

    speedbump Previous member

    Messages:
    4,540
    Location:
    Riverview, Fl.
    Amen! Amen!
  4. Spaceman Spiff

    Spaceman Spiff Architect

    Messages:
    277
    Location:
    Salt Lake City, Utah
    I'm a recovering do it yourself addict, and there's a list of things I don't do.
    Drain augering
    concrete
    well pumps (mine is at 325' too)
    well drilling
    drywalling more than 1 room
  5. Bob NH

    Bob NH In the Trades

    Messages:
    3,317
    Location:
    New Hampshire
    Additional information you need to select the pump is the water level in the well (measured from the surface) when you are pumping. That is the important factor in selecting the pump, rather than the depth of the hole.

    If the water is within 100 ft of the surface when drawn down you need a different pump than if the water is 250 ft from the surface. The difference is about 65 psi.

    A 1/2 HP pump suggests that the water level is pretty high in the well. A Goulds 5GS05 delivers 5 GPM at about 285 ft of head and 4 GPM at 320 ft. Subtracting 60 psi (about 140 ft) for the tank and pipe losses suggests about 150 ft to water.

    A 1 HP 10GS10 would deliver 10 GPM at the same conditions.

    The well test records should specify the drawdown corresponding to the 20 GPM capacity.

    If you know the model of the existing pump you can match the pressure capability with a larger pump. If you don't know the model of the pump, you can get a fair idea of the depth to water by testing the pump.

    Shut off all flows except a faucet where you will run water for test. Then let the pump run and adjust the valve so the pump maintains a pressure on your tank gauge about 3 psi below shutoff pressure and measure the flow rate with a 5 gallon bucket and a watch. Repeat it at a pressure near the START setting of the switch. With those flow rates and your pump horsepower you can select a larger pump that will do what you want.

    When you put in a bigger pump you need to plan how you are going to control it. You will need a bigger tank or a CSV. With a bigger pump, you will use more power if you throttle it with a CSV. There are differences of opinion among those who post here about what is appropriate.
  6. Kendallroad

    Kendallroad New Member

    Messages:
    14
    Kendallroad

    My wife agrees with SpacemanSpliff.
    Just one more question before I surrender.
    How do you disconnect the 1 1/4 in. PVC pipe from the 1 in. poly line that goes underground to my house? I removed the well cap and saw the line that holds the pump. At that time, I did not move the wires to look for the pvc pipe fitting.

    Thanks to all the responders.
    Kendallroad
  7. Bob NH

    Bob NH In the Trades

    Messages:
    3,317
    Location:
    New Hampshire
    There is usually a "pitless adapter" that connects the pump to the line going to the house.

    The top one of the two in the document at the link is typical for a submersible pump.

    The pump is lifted out and disconnects from the adapter when it is raised. You may have to get a piece of pipe for a pull pipe for the pitless adapter unless there is a lifting mechanism left attached when the pump was installed.

    You will need to look at your system to see if that is what you have.

    http://www.merrillmfg.com/about/installation/products/02-PitlessUnits/PitlessAdapter.htm
  8. Kendallroad

    Kendallroad New Member

    Messages:
    14
    Well capacity test results

    The 20 gpm rating was the well drillers air pump test with the draw down to 325 ft. The static water level was 15 feet below the top of the casing (BTC).
    The pump installed was a Goulds 7GS05 having max. capacity of 10 gpm.
    The average draw down at a rate of 5 gpm was 60 feet BTC.
    For a varity of reasons ,ie, drop in water table, high insoluble iron deposits, I calculated the draw down to now be about 210 feet. This is based on a test that showed a pump capacity of about 4 gpm at 10 psi pump pressure, using the pump manufacturers performance curve.

    I know believe that a 7GS10 pump is the correct unit to be installed.
  9. Gary Slusser

    Gary Slusser That's all folks!

    Then that is the recovery rate of the well. And doing some simple math... unless my mind and calculator are both malfunctioning... you have a 20 gpm recovery rate and pump out at 5-10 gpm! There is no draw down then.

    So... how did you calculate 210 feet "draw down" or they come up with the 60 feet?

    What are "insoluble iron deposits" in a well, and where are they to be able to reduce recovery rate water flow?

    Running water through a 1/2" or 3/4" hose bib or boiler drain valve at the pressure tank tee is not giving you an accurate figure of the max gpm of the pump and is only valid at that faucet and certainly not at your 'average' psi.

    Why are you wanting to replace this pump?

    Is this a fully cased and screen well or rock bore?
  10. Bob NH

    Bob NH In the Trades

    Messages:
    3,317
    Location:
    New Hampshire
    The 7GS05 delivers 4 GPM at about 265 ft of head per my curves. The pipe losses at 4 GPM are probably less than 10 ft.

    265 ft - 10 ft head loss - 23 ft = 232 ft, so 210 ft is pretty good.

    Using 20 head loss for a higher flow, and the full 232 ft of drawdown, and 60 psi (139 ft) the total head would be 371 ft, at which the 7GS10 would deliver about 7.5 GPM.

    If the 7GS05 delivers only 4 GPM at 10 psi at the pump head then, assuming that the 7GS05 is in good condition, the 7GS10 looks like the right choice for replacement.

    You should try to directly verify the drawdown level because either a worn pump or increaed drawdown would produce the observed result. If the problem is a worn pump then the 7GS10 replacement would work but it might not be the best choice.
  11. Gary Slusser

    Gary Slusser That's all folks!

    I say if he has a 20 gpm "capacity" (meaning recovery rate) and neither pump delivers more than 10 gpm, there is no draw down. The water level will remain at 15' or wherever the water table is at the time. The "Capacity" would have to fall by over 50%, to less than 10 gpm, before there would be any draw down.

    Do we know that his power cable is capable of operating a 1 hp pump?

    Do we know if his 1/2 hp isn't a 110 due to a 15' static water level?

    Does he know that a 6" well has 1.47 gal/ft of water in storage and that his 210' draw down is probably never going to happen unless there is a multi year and extensive drought or he has a 4" dia well or smaller?

    So I see no need to go to a larger hp and gpm pump and I ask again, why is the current pump being replaced?
  12. Bob NH

    Bob NH In the Trades

    Messages:
    3,317
    Location:
    New Hampshire
    Capacity of a well usually depends on drawdown.

    When the water is at the "static" level there is "zero" recharge. When the level drops below the static level there is a potential (head) to refill the casing. The variation of recharge rate between the static level and some other level is not always linear. A well that has 20 GPM recharge rate at a drawdown of 300 ft below the static level may have a much lower recharge rate when the drawdown is 200 ft and the head that is available to push water through the aquifer is 100 ft less.

    If one accepts as valid the owner's report that a Goulds 7GS05 produces only 4 GPM with 10 PSI at the well head, then one must conclude that the drawdown is on the order of 230 feet below the surface. (See my analysis of the allocation of available head.)

    My concurrence with his choice of pump to deliver his pressure needs from the lower level in the well included a suggestion the he verify the actaul water elevation in the well for the pumping condition. If the measured elevation is down in the range of 200 ft below the surface as suggested by the test, then he indeed needs a pump that delivers more head.
  13. Gary Slusser

    Gary Slusser That's all folks!

    Yes, and none of us knows the actual figures without a pumping test, so we are left to make assumptions.

    Where do you see him saying he got 4 gpm at 10 psi "at the well head", I can't find that?

    And if he didn't get it at the well, and got it at some 1/2" or 3/4" hose bib etc., all the rest of this is pure assumption.

    I don't think there was an accurate test and certainly not any form of a pump test using the drop pipe output which requires lifting the pump. And... he said: I calculated the draw down to now be about 210 feet. This is based on a test that showed a pump capacity of about 4 gpm at 10 psi pump pressure, using the pump manufacturers performance curve.

    That's quite a bit different than doing a real pump test and actually measuring the water level the test was run at.
  14. Kendallroad

    Kendallroad New Member

    Messages:
    14
    Pump capacity test method

    To test the capacity of my well at this present time, I constructed a 3 cu. ft.box fitted with a 90 degree square notched weir. the box was located with- in 10 feet of the valve at the bottom of my pressure tank. I connected a pressure gauge to a tee at the end of the 10 foot length of 5/8 in hose and attached a wool sock to the end to disperse to flow. the flow was calculated using the discharged tables for 90 degree notched weirs from an engineering hand book. the flow rate reported was that obtained when the pressure held steady for 15 minutes with the discharge valves wide open. the pressure gauge at the pressure tank was about the same as the reading as the pressure gauge on at the hose.
    I did this test to try to back calculate the well's draw down from the pump' curve.

    I would again like to thank all of the responders in my quest to make a decision baised on fact rather that feeling.

    Kendallroad
    Last edited: Mar 9, 2008
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