I'd like to optimize my well water system...help needed.

[bjm999]

I didn't rerun the test with the gauges swapped.  I can do that though.

Wow, down to 2 GPM....that's pretty good!  Would 2 GPM be enough to keep the pump cool or create any other issues?  Would I be able to take it up to 65 or 70 PSI while still having constant pressure down to 2 GPM...or maybe 3 GPM?  That may just be enough pressure to allow me to install a backflow preventer that is probably needed for my irrigation.

[Cary Austin]

Yeah you will lose another 10 PSI through a backflow preventer.  Maybe required, but a vacuum breaker would not cause friction loss.

I will look up some pump curves.  The trick to getting a 5HP to stay cool at 1.7 GPM is finding one that has a good drop in horsepower when restricted with the CSV.  If the amps drop by 40%-50% the motor is de-rated enough to safely pump hot water, so it takes very little cool water to keep them happy.

[Cary Austin]

See how this 5HP will drop to 2HP load at low flow?  This pump/motor needs very little cool water to keep it happy.

[bjm999]

This makes a lot of sense.  That would be a nice setup and probably last a long time.  From my quick googling that's not going to be a cheap fix.  Is changing a well pump that may be 300 feet or more deep something the average homeowner could do?  I'm guessing a pro would charge several thousand to make that change.  May be hard to talk the wife into do that. 

[Cary Austin]

Yeah looks like one of those 45S50-12 pumps with a 5HP motor would cost almost 4K.  But your well pump cannot be 300' deep from those specs.  I would guess 150' or so.  I would be guessing another 1K for the labor if you can't do it yourself. 

[bjm999]

Are you guessing the depth to water is around 150ft or the actual pump depth is around 150ft?

[Cary Austin]

The water level has to be around that depth, and the pump doesn't need to be set much deeper than that.  I am guessing less than 200'.

[bjm999]

Yeah my understanding from the guy the installed the well, the depth to water is around 160 but due to water quality the pump is around 350 ft deep.  Would that make sense based on the data from this thread?

[Cary Austin]

Maybe.  But that pump won't make 60 PSI to shut off from 350'.

[bjm999]

Maybe that's the problem then.  Maybe the pump was just undersized.

[Cary Austin]

No question the pump is undersized for what you want to do.  That has been the problem through all of this.