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Thread: Goulds GT10 and Pressure Tank

  1. #1

    Question Goulds GT10 and Pressure Tank

    Been having a heck of a time with well system that is used for irrigation only and would like to ask some advice. There is a submerged pump that feeds a 1500 gallon tank from which the GT10 (1HP) and pressure tank use for the sprinklers. After sprinklers shut off the pump pressure will not go any higher than 50psi even after playing with the pressure switch to allow the pump to stay on...basically I'm not getting enough pressure....any ideas? Is the pump shot?
    Last edited by CSU_Ram; 03-01-2006 at 12:30 PM.

  2. #2
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    You didn't say if the sprinklers work good or not. If not, the pump is not properly sized. If your pump in a self priming centrifugal (I don't know Goulds model numbers.) it will not build more than 50 psi. A jet pump won't do much more than 65 psi.

    Adjusting the pressure switch won't make the pump go higher in pressure.

    bob...

  3. #3
    In the Trades Bob NH's Avatar
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    The Goulds GT10 is a single stage centrifugal pump that is usually used for irrigation and sprinkling. It has a shutoff head of about 51 psi. You would typically operate it at about 35 to 40 psi at which head it would give you 30 to 35 GPM if operating from a tank with flooded inlet to the pump.

    You should determine the GPM and pressure you need, and determine if you can use a single stage or if you need a multistage pump.

    If you need more pressure and high flow, you will need a multistage centrifugal, or a larger single stage centrifugal that will also give you much more flow (perhaps 60 to 80 GPM). If you want a really lot of pressure, you may want to use a submersible, which has special considerations when used in a tank.

    If you need only a bit more pressure and limited flow, you can use a shallow well jet pump.

    The correct process is, determine your needs (flow rate and pressure), and then select the pump to do the job with a bit of margin so you won't be disappointed when the pump wears a bit and you have more pipe losses than expected.

    Using a pressure switch that turns the pump on and off while the irrigation system is running can be disappointing because you have a lot of variation at the limits of the pressure switch settings. It is best to try to match the sprinkler demand to the pump and use the pressure switch only to turn the pump on when the sprinklers come on and shut the pump off when the sprinklers go off. Match your sprinkler flow, pump flow, and switch settings so the pump is running steadily at the required pressure and flow when the sprinklers are on.

    If you are operating near the most efficient operating point, you can cut back the flow (number of sprinkler heads) until you get the pressure that you want (within the capability of the pump) and the pump will run continuosly at contant pressure until you shut off the sprinklers.
    Last edited by Bob NH; 03-08-2006 at 10:29 AM.

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    I only disagree with one thing, the pressure switch. You may have noticed the centrifugal pump did not come with one. This is because self priming centrifugals are not compatible with a pressure switch. Use a pump start relay to start and stop the pump with the sprinklers or you will simply have motor and melted pipe problems.

    bob...

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