low submersible well pump pressure

Discussion in 'Pumps and Tanks Well Forum & Blog' started by unk, Aug 15, 2008.

  1. unk

    unk New Member

    Messages:
    6
    Hi,
    I just purchased a property, it sat empty for approx 2 1/2 - 3 years.
    I know the water system was not winterized properly as when I first started the pump I had broken pipes. I have replumbed the whole house with cpvc.
    I was wondering if you can help me understand my well/pump system, then maybe help me look for a problem with my pressure, or lack of?
    I have a 3/4 hp submersible pump 37 ft in a 4 inch cased well. Thinking my pump had been running constantly, I changed the pressure gauge. It was reading 20-25 lbs, still the same pressure with new gauge. I then installed a new pressure tank, due to not being able to get a pressure reading on the old one. Installed was a new 25 gal vertical tank with a new 40-60 pressure switch. Still no increase in pressure. I then dug for the pump, down 4 1/2 ft. I pulled it to see if the screen was plugged or any noticeable problems. The screen was ok as well as the pump, checked all clamps and returned the pump to the casing. My pressure is still 20-25 lbs.
    As instructed to do, I placed a gauge at the well top thinking I may have a leak in the pipe leading to the house. The pressure reads 25 lbs at the pump so no leak. Can I assume my pump is going bad. Which is something I don't understand. Is it not turning fast enough or maybe some seals or the like have gone bad. Could it be the time the property sat empty and the pump got corrosion build up (which I noticed when I pulled the pump) from just sitting in the well?
    Thanks in advance for your help.
  2. Bob NH

    Bob NH In the Trades

    Messages:
    3,317
    Location:
    New Hampshire
    Another possibility is that there is a leak in a pipe that is losing enough water cause the pump to operate at a the far right of the curve where the head is low.

    With such a shallow well I would pull the pump and check the flow and pressure. You could start by disconnecting the pipe to the house and check the pressure at the top of the well. If that is high then you may have an underground leak. If that is low, pull the pump and run the test.

    DO NOT shut the valve completely.

    A properly sized 3/4 HP pump for that depth should produce somewhere in the range of 10 to 13 GPM at 60 psi. It should easily produce 100+ psi.
  3. unk

    unk New Member

    Messages:
    6
    Thanks Bob,
    Maybe I didn't express myself properly but I have checked the pressure at the top of the well, it is 25lbs. I did that due to thinking I had an underground leak in the 15ft from well to the basement entry.
    Maybe I missed something but what do you mean by " if the pressure is low, Pull the pump and run the test"? also, DO NOT shut the valve completely ?
    Sorry but I am not understanding those 2 previous items.
    Thanks for your help/replys as this is really getting frustrating.
  4. Bob NH

    Bob NH In the Trades

    Messages:
    3,317
    Location:
    New Hampshire
    I may have misunderstood what you said.

    By checking the pressure at the top of the well I mean to disconnect the pipe to the tank AT THE WELL, and put a valve on the pipe coming from the well, with a pressure gauge in a tee between the pump and the valve. You probably don't need larger than a 1" valve and a full-port 3/4" ball or gate valve will work.

    With the valve about 1/2 open (full open if a 3/4" valve), start the pump. Then while closing the valve, read the pressure gauge. If the pump is working properly and there is no leak between the valve and the pump the pressure should increase to at least 60 psi, and to 80 or 100 psi if you keep closing the valve.

    You must restrict the flow (that is the reason for the valve) in order to develop rated pressure.

    If the pressure in the test described substantially exceeds the 25 psi you have been measuring in the tests that you described, then there is a leak in the pipe between the well and the tank, which has been disconnected for the this test.

    If the pressure doesn't get to 60+ psi then you might as well pull the pump because either the pump has failed or there is a split in the down-pipe.

    I said to not close the valve completely (in the test described above) because most submersible pumps will develop 150 psi or more when there is no flow. That could cause the pipe to fail or come off a fitting. That is a condition that you should avoid.

    If you have already tested it as I have described and still have only 25 psi, then pull the pump.
  5. unk

    unk New Member

    Messages:
    6
    Bob,
    Yes, I have tested it the way you have described. Only 25psi on the gauge with valve totally closed. As I mentioned there was quite a bit of corrosion build up on the pump itself when I pulled it, I had to scrape/chisel it with a screwdriver. Will a pump go bad sitting in the water for 2 1/2 - 3 years when not in use. Is it the fact the pump isn't turning fast enough or what?
    I know your not a magician, but is there anything that would make it go bad but not all at once quit working? I've always assumed a pump just quits. Thats what has been most frustrating.
    Thanks
  6. speedbump

    speedbump Previous member

    Messages:
    4,540
    Location:
    Riverview, Fl.
    I think you said the Pump was running for a long time and wouldn't shut off. The impellers in that Pump are almost positively plastic. When a Pump runs without moving water, it gets very hot. So does the water. This melts and deforms the impellers and diffusers in the Pump. This is why it won't build any more pressure. You need a new Submersible Pump

    bob...
    Last edited by a moderator: Jul 10, 2011
  7. unk

    unk New Member

    Messages:
    6
    Thanks Guys for all your help and patience. It was very nice to see answers for my questions, even though they may have seemed a bit trivial. One last question, which brand(s) 3/4 hp submersible (if a 3/4 hp is adequate with 2 full bath) pump would you recommend?
    Thanks
  8. Bob NH

    Bob NH In the Trades

    Messages:
    3,317
    Location:
    New Hampshire
    A Goulds 10GS07 (3/4 HP, 10 GPM Rated model) will deliver 13.4 PM at 60 psi and 15.9 GPM at 40 psi from a depth of 40 ft. That is more than your tank is sized for. The 25 gallon tank will have a drawdown of about 8 GPM between 40 and 60 psi so the pumping time will be about 40 seconds, which is shorter than recommended.

    A 10GS05 will give you 9 GPM and a 7GS05 will give you 9.3 GPM under the same conditions.

    I would select the 10GS05 which will deliver 13.4 GPM at the 40 PSI start setting of your pump. That is plenty for 2 showers and a washing machine. The pump will not shut off at 60 psi if flow exceeds 9.0 GPM.



    Goulds pump tables and curves are at the link. You can find similar pumps at Speedbump's site and compare performance.
    http://www.goulds.com/pdf/7310.pdf

    You can buy the Goulds at http://www.wwpp.us/goulds/goulds-submersible-2-wire.shtml
    Last edited by a moderator: Aug 18, 2008
  9. unk

    unk New Member

    Messages:
    6
    Thanks for your recommendation Bob, what is the difference between the Gould and the below Wayne 3/4/hp pump I found at my local home improvement center?
    Obviously name brand, but me, as a novice don't see any difference. Both are Stainless steel, 12gpm @80 ft, same hp.. etc.
    Thanks in advance for your clarification.
    Last edited by a moderator: Jul 10, 2011
  10. Gary Slusser

    Gary Slusser That's all folks!

    The Wayne or any other big box store brand pump is nowhere near close to the quality of a Goulds or other major pump brand.
  11. Bob NH

    Bob NH In the Trades

    Messages:
    3,317
    Location:
    New Hampshire
    You can get a lot of 3/4 HP pumps that will deliver 12 GPM at 80 ft.

    I can't find the GPM vs flow data for the one at the link you provided.

    Check the link and read the review.
    http://www.google.com/search?q=wayn...ox&ie=UTF-8&oe=UTF-8&sourceid=ie7&rlz=1I7TSHA

    The one at the link looks like your example where the curve seems to pass through about 720 fallons per hour at 80 ft on the curve. Note that the pressure is only at 50 psi vs 60 psi for the 3/4 HP Goulds pump that I gave you the link for.

    Here is a link that I found for the Wayne pump.
    http://www.waynepumps.com/Spec/DWS_Series.pdf
    Compare the Table to the Table for the Goulds pump.
  12. unk

    unk New Member

    Messages:
    6
    Thank you Bob,
    The url's you posted helped me understand the why better. I really do appreciate your time and experience as it walked me through what I thought was right but with more confidence. I do appreciate you sharing with me why you recommended what you did instead of "just because" or "it's name brand".

    In a previous reply you mentioned Speedbumps site, is that for ordering a pump/supplies or simply a reference site?
    Thanks
  13. Bob NH

    Bob NH In the Trades

    Messages:
    3,317
    Location:
    New Hampshire
    You can buy pumps from him. I think you can do it on the site but I would call and discuss the requirements with him.
  14. valveman

    valveman Moderator Staff Member

    Messages:
    4,391
    Location:
    Lubbock, Texas
    A ½ HP pump will cycle on and off if you are using less than 9 GPM. A 3/4 HP will cycle if you are using less than 12 GPM. The 25 gallon tank you have is not large enough to keep you under the maximum number of cycles per day allowed. You can use an expensive 80 gallon tank that will keep you within the acceptable number of cycles. Or you can use a Cycle Stop Valve that will actually solve the cycling problem, not just reduce it a little bit. With a CSV, the 25 gallon tank is plenty large enough.
  15. Gary Slusser

    Gary Slusser That's all folks!

    And today, many 2-2.5 (or more) bathroom houses (with large tubs and showers) will require more than 9 or 12 gpm for their peak demand flow rate. So I do not agree with sizing a pump just to keep it from cycling. I suggest the CSV way or to live with short cycling as a cost of living.
  16. nhmaster

    nhmaster Master Plumber

    Messages:
    3,189
    Location:
    S. Maine
    Bet ya all a cold one the impellers are either melted or plugged or worn out.
  17. speedbump

    speedbump Previous member

    Messages:
    4,540
    Location:
    Riverview, Fl.
    +

    I'm with ya on that one.

    bob...
Similar Threads: submersible pump
Forum Title Date
Pumps and Tanks Well Forum & Blog Submersible pump well problem Today at 6:25 PM
Pumps and Tanks Well Forum & Blog Protecting a submersible pump using flowmeter Saturday at 7:49 AM
Pumps and Tanks Well Forum & Blog Tankless Submersible Well Pump losing pressure Jul 7, 2014
Pumps and Tanks Well Forum & Blog Submersible Pump Problem Jun 30, 2014
Pumps and Tanks Well Forum & Blog Submersible Well Pump Dying? Jun 25, 2014

Share This Page