Well Pump GPM which is correct?

I need to install a new submersible well pump. My well delivers about 3 gpm but pump is about 60 feet below water level. My 35 gal. bladder type tank has a 12 gal. drawdown set for 20/40 lbs. Should I pay more for a 5gpm pump instead of buying a standard10 gpm pump? I have an electronic sensor to turn off the pump if it sucks air. Thanks for you insite to this question. Regards, Henry
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3 gpm

tank
pump? I

That is not how you size a pump. You calculate the total dynamic head at the pressure you want to use and then select the hp to do the job. Start yer lernin' here: http://www.jessstryker.com/pump.htm
A 6" well has 1.47 gal per foot of water. Your 10 gpm pump moves what water it can based on the head and the water level in the well and then your 3-5 gpm recovery is added to the well (per minute), so you really have to use a lot of water to have a problem. The gpm rating of a pump is all about the TDH. A 1/2 hp 10 gpm is probably what you had and will work just fine as long as you aren't at a couple 1000' or more above sea level.
Gary Quality Water Associates
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Gary, Thanks for you comments. I had been putting the low capacity pumps in before at the suggestion of earlier documentation. What does TDH stand for? Thanks again.
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TDH = Total Dynamic Head a.k.a. the height from the water level to the point of use, plus the required pressure expressed in feet of head (I think - back me up here gary)
Dean
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point
think - back

You're correct.
Gary Quality Water Associates
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Thanks for the education on TDH and pump curves. In all the pump literature put out with the submersible pumps never have a pump curve chart. Their only chart shows a low yield pump pumping less water at 20' but more water than a normal pump at say 150'. For my use on their chart the normal, 10 gpm, will pump 8.6 gpm at 40# from 100', which is about what I need. I now know not to spend extra for the low yield pumps which I don't need. Thanks again guys. Henry
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