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Thread: 1/2hp or 3/4 hp pump?

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  1. #1
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    Jun 2014
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    Southfield, Michigan, USA.
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    1/2hp or 3/4 hp pump?

    I ran out of water in the house I recently bought. I thought it might be the pump, so I replaced the 3/4hp Wayne pump with a spare 1/2hp Simer I had. I was able to get it primed finally, but the pump still seemed to struggle so I called the well guy out. He pulled and replaced the point (the house had been mostly unused for 3 years, so the point was somewhat clogged). He tested the output and told me I'm getting 5.5gpm. The well is 25' with a 4" casing, water level is at 6'. I have a good size tank, abut 30gal. The 1/2hp pump has a 20psi on, 40psi off switch, so I reset the tank pressure to 18lb. The pump usually runs for about 3 minutes, which is fine. But the 3/4hp pump had a 30/50 switch, and more pressure would be nice. However, I am worried the bigger pump may outrun the well and lose it's prime, which is what I think happened in the first place. With the new point, am I ok putting the 3/4 hp pump back in, or should I stay with the smaller pump so I never outrun the well? Thanks in advance for any tips!

  2. #2
    Pump guy speedbump's Avatar
    Join Date
    Jun 2005
    Location
    Murphy, NC. USA.
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    11,735
    The only reason for a larger pump that is on a well that only gives 5.5gpm would be for the pressure. Sometimes a 1/2hp shallow well jet will do more pressure than a larger horsepower jet. It all depends on the impeller diameter and the nozzle/venturi sizes. If you have a Square D type switch, with the pump running and all water turned off, take a pair of pliers and hold down the plate that the spring/s are pushing down on. This will prevent the switch from turning the pump off. Let it run until it won't make any more pressure. If it makes it past 50 psi, crank down on the 3/8" nut to raise the switches settings to 30/50.

  3. #3
    Newbie
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    Jun 2014
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    Southfield, Michigan, USA.
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    Great - thanks! I knew which nut was to adjust the pressure, but hadn't found a simple method like this to determine how to determine the system's overall capability!

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