Goulds GT15 (1.5 HP shallow well pump) won’t build pressure above 40psi

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Cavedan

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I pump from a relatively clear creek. Pump sits about 15, maybe 20, feet above intake. Intake line is about 50 feet long. Foot valve installed at end of intake line. No leaks along intake line. Pumps goes uphill to pressure tank maybe 10 feet. From pressure tank to irrigation lines, maybe another 10 feet of head. Hard to estimate how much irrigation line. Maybe a half mile worth of underground 3/4” pipe. Pressure tank has no outside leaks, but there might be a slow bladder leak (over two years the psi dropped from 18 to 15).

Two years ago, when I replaced a 2hp model that had burned out, I was only able to get this model to reach 40 psi so I set the cut in to 20 and cutout to 38. Yesterday I found the same problem persists after trying to set it to 30-50. If left to it’s own devices in this scenario, the pump will reach 40 psi, then after a few minutes it will start to audibly struggle and slowly lose psi.

I’m at a bit of a loss here. My initial thinking is that I might have too much underground line for a 1.5 hp pump. Is there anything I’m overlooking?
 

Reach4

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Goulds GT15 is not a jet pump. It is a single stage centrifugal pump made for high gpm rather than higher psi.
Looks like at 35 to 40 psi, it is generating more pressure than expected. I think a 2-stage sprinker pump may be a better choice.

Irrigation pumps are usually run without a pressure tank or pressure switch, and you select the emitters to match what the pump can do. You turn the pump on and off by a timer or manually.

This is not going to do well with impact sprinklers.
 
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Cavedan

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Goulds GT15 is not a jet pump. It is a single stage centrifugal pump made for high gpm rather than higher psi.
Looks like at 35 to 40 psi, it is generating more pressure than expected. I think a 2-stage sprinker pump may be a better choice.

Irrigation pumps are usually run without a pressure tank or pressure switch, and you select the emitters to match what the pump can do. You turn the pump on and off by a timer or manually.

This is not going to do well with impact sprinklers.

Ah, thanks. That makes sense. The previous owner had a gt20 set up and it was able to pull up a decent enough psi. But clearly not the right tool for the job. We’ve mainly switched to drip irrigation and run the occasional rain bird. I’d just like to see a higher psi for certain applications, like an outdoor shower that struggles when the psi gets into the low 20s.
 

Cavedan

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Goulds GT15 is not a jet pump. It is a single stage centrifugal pump made for high gpm rather than higher psi.
Looks like at 35 to 40 psi, it is generating more pressure than expected. I think a 2-stage sprinker pump may be a better choice.

Irrigation pumps are usually run without a pressure tank or pressure switch, and you select the emitters to match what the pump can do. You turn the pump on and off by a timer or manually.

This is not going to do well with impact sprinklers.
Can you recommend a brand and pump that would be a better fit? Currently my house/spring system runs a J15s, would something like that be a better choice.
 

Cavedan

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Yes the J15S has a max pressure of 83 PSI where the GT15 can only make 51 PSI and won't work with even a 30/50 pressure switch.
Does the GT20 provide more pressure than the GT15, or is it just increased flow. If I remember correctly, I when our irrigation was run from a GT20, we were running higher pressure, but I can’t quite remember to what degree.
 

Valveman

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Does the GT20 provide more pressure than the GT15, or is it just increased flow. If I remember correctly, I when our irrigation was run from a GT20, we were running higher pressure, but I can’t quite remember to what degree.
A GT20 can only build 56 PSI max, and I still would not use it with a 30/50 switch, just 25/45 at most.
 
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