how much difference does 1/2 hp make in pumps?

rbig · Jan 13, 2010

I have a well I'm working on. It's on my son's place, and had a 2hp Sta Rite shallow well pump on it. It feeds two sprinkler sections of 4 heads ea.

The pump ate itself. Nothing but slag and spewed parts. They run $400 and upward.

I've got a guy who will sell me a 1.5hp Sta Rite for $100.

Will I probably do OK going with the 1.5hp one? I have no idea if this makes a big difference or not in these situations.

Gary Slusser · Jan 13, 2010

Pumps come in two parts, the wet end that moves the water and the motor that makes that happen.

The wet end is rated in gpm and the motor in hp. You can get various gpm and use the same hp motor so, you need to know how many gpm you need and then you select the number of horses to get the job done. So find out the gpm rating of each and IF the 1.5 hp will deliver the same gpm at the same psi range that you run the old pump at.

Sponsor · 2022-01-29T12:20:58-0800

iconicplumber · Jan 13, 2010

pumps are rated on a curve, and every pump should be supplied with a pump curve chart.

with most pumps, as ft. of head increase, gpm decreases.

calculate your head loss and your gpm requirements and compare to pump curve. if it falls into your range you should be ok.

but as the water softner guy said every pump is different so check it out

NHmaster · Jan 14, 2010

And don't buy a Sta-Rite, it will just happen all over again.

Thatguy · Jan 14, 2010

rbig said:
I have a well I'm working on.
Will I probably do OK going with the 1.5hp one? I have no idea if this makes a big difference or not in these situations.

How deep is the well?

Here're the formulas

HP = horsepower, HD = head in feet, EFF = efficiency in percent

GPM = HPx40xEFF/HD
HD= HPx40xEFF/GPM
EFF = HDxGPM/[40xHP]
HP = HDxGPM/[40xEFF]

E.g., 100x120'/[40x50%] = 6.1 hp
"A survey of popular pump brands demonstrates that pump efficiencies range from 15% to over 90%"

rbig · Jan 14, 2010

Well, basically, I'd lose .25 of capability. If these wells were maybe over specced at 2.0hp, that wouldn't be much of a loss. If it were slightly under specced at 2.0hp, going down a .25 in capability would be a sizeable loss. Does this make sense?

Gary Slusser · Jan 14, 2010

Start at Pressure versus flow at the bottom of the page in the link below.

http://www.irrigationtutorials.com/pump.htm

NHmaster · Jan 14, 2010

rbig said:
Well, basically, I'd lose .25 of capability. If these wells were maybe over specced at 2.0hp, that wouldn't be much of a loss. If it were slightly under specced at 2.0hp, going down a .25 in capability would be a sizeable loss. Does this make sense?

You need to know the depth of the well, the static level of the well and the recovery of the well as well as the gpm requirements of the sprinkler system to make an informed choice. The old pump may have self destructed because it ran dry.

Masterpumpman · Jan 17, 2010

Smaller HP!

You will probably notice a drop in flow with a lower HP motor.

Others have said here that it depends on the pump design curve and they are right. I'm just trying not to be to technical.

$100.00 for a 1.5 hp pump sounds better than $400.00 if it will do the job. You won't know unless you gamble $100.00.

As far as the brand, I love Sta-Rite Pumps, Goulds, Flint and Walling and other major brands.

Some people like Fords and some like Chevrolets and a few don't know the difference! Personally I'm a Ford (Sta-Rite) man.

Porky Cutter, MGWC
Master Ground Water Certified by the NGWA
www.dci-inc.us

DamoJackson · Jan 11, 2011

Hi Rbig

I wouldn't pay anything more than $120 for a pump for what you need it for. Online is obviously a good place to start, or Amazon.

Good brands are Simer, Flotec or Wayne which I'd go for! I've had a Wayne which was passed down from my Father, it's at least 30 years old, still works fine.

I don't know if you've got this sorted out yet, as I've just joined the forum but, shoot me a pm if you need any installation tips.

Regards

Justwater · Jan 11, 2011

hate to break it to you buddy, but 30 years ago people took pride in their craftsmanship. any pump you pay 130$ for now is a POS. you get what you pay for with these products. you just named the 3 cheapest made pumps IMO.

Texas Wellman · Jan 11, 2011

Considering that the thread is dated from Jan. 2010 (last year) I think he's spamming...

how much difference does 1/2 hp make in pumps?

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