Your opinion on my pump choice- deep submersible.

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Odysseus99

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Hi guys-
I think I've narrowed down my pump choice, but I just want to pass it by more experienced minds, see if I'm missing anything, and ask a question.

Well depth 400', produces 30 gpm no sand or grit, static level 290' below head, pumping to a cistern not a pressure tank, vertical rise to cistern from head 35', total vertical rise 325'.

Total length of pipe from pump to cistern 660', with 1" pipe, about 6 fittings, so total dynamic head 360 ft. or so.

Ive been looking at Flint and Walling 1 horsepower pumps, either 5 or 7 gpm. Here's the charts:

http://www.deanbennett.com/4inch-submersible-pump-capacity-charts.htm

So first, does it look like I'm in the ball park? Missing something?

Second, I'd prefer the 7 gpm so I'm using my generator less to fill the cistern. What I'm wondering is, would the 5gm pump probably last longer? since it is being strained less-

Thanks
 

Reach4

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It looks to me as if you have selected a good match with the 7 GPM 1 HP. I don't know about the longevity. I expect that will be affected by the size of the cistern. I would think you might still have a float switch to cut the water, in case you fall asleep with the generator running. My comments are not based on experience.
 

Odysseus99

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Thanks Reach and Valveman. I'm all for fewer parts to wear, Valveman. I guess you are saying that operating slightly left of the curve is not a significant strain on the motor. I guess I don't understand how these pumps work- fewer impellers, faster rate of flow. So be it.

So, why would someone use a lower rate pump? If they had a very high total head, or if they have a flow rate in the well not high enough to handle a higher rate pump, right?

Yeah, I'll take a 10 gpm, even if it only operates at 9. I figured by using a lower rate pump I'd be straining the motor less and thus it would last longer, but maybe that's not the case. Perhaps so long as you use a pump close to its efficiency point on the curve, its going to last as long as any other, so you might as well get the highest flow rate pump you can given your wells production rate, and the hp of motor you are willing to pay for (and the wire- I'll spend $1000 on #8- whew!)

Glad I told the driller to go the last 20 feet. That's when the production rate went from 8-10 gpm to 30 gpm after we got into the serpentine.
 

Reach4

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It is good to look at the pump curves. Here is the same info in table form. A 7 GPM pump might do better if the water level in the well dropped. A 7 GPM pump could generate more pressure at the surface, but you don't need significant pressure at the surface.
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You would use the 0 PSI rows on the tables.
 

Odysseus99

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Thanks Reach and Valveman. Erring on the side of caution I think I'll go with a 7 gpm, on the chance that the drought here in California will continue and my static level drops significantly.
 
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