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Thread: Determining flow rate of well

  1. #1

    Determining flow rate of well

    I need to determine the recharge rate of a well to be sure that it has the capasity I need. The well is 50 yr old with 30" concrete pipe casing . It is 30 feet deep with 16' of water. I tried to find a smaller pump with 25 GPM with no luck. The smallest I can find is 4000 GPH. If I pump it down and then time how long it takes to refill will that give me an accurate flow rate? Do I need to do it several times to be accurate?

  2. #2
    Pump guy speedbump's Avatar
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    I don't really what would be that accurate Art. You are buying centrifugals not jet pumps. For instance, a 1/2hp jet pump max's out at around 12 gpm, a 1hp at 25. A centrifugal starts at 3/4hp and will do around 60 gpm. The way to do this is to put a valve in the discharge line of the pump and keep closing it off until you get the pump to pump a steady stream with the water level at around 20 feet. Then measure your gpm once you have it adjusted.

    bob...


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  3. #3
    Your reply confused me. I want to find out the GPM that the well will support.

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    Pump guy speedbump's Avatar
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    Do what I said at the end of my post. No matter what pump you have, just restrict the output of the pump until the pump and the well seem to be happy at around a 20 foot water level.

    bob...


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  5. #5
    I realze that. What I am trying to guestsmate is the GPM I will get from the well without pumping it dry.

  6. #6
    Pump guy speedbump's Avatar
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    I don't kow what your not understanding.

    Hook up the pump with a valve that you can regulate on the output of the pump. Start the pump, as the water level starts to go down, close the valve slowly until you get the pump to keep pumping with about a 20 foot water level.

    Or if you really want to get exact, just put a droppipe in the well 30 feet long, turn on the pump, wait until the water level drops to 25 feet. Now what you have coming out of the pump is all the well will produce.

    bob...


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