Help selecting pump and poly for well 440’@7.5gpm & 155’ static.

[Simple_Jack]

Hey everyone, I did all of the reading on here I could before my brain got full and I have to ask questions.



Well is drilled to 440ft with a refresh rate of 7.5gpm from the bottom, static water is at 155ft. From the well to the house I have 340ft of 1-1/4” poly with no elevation change where I have a CSV and 10 gallon pressure tank. Water usage should never exceed the refresh rate, it’s just me and my wife in a 2 bedroom house with no irrigation. I think I want to set the pump at 300’ if the poly can handle it.



Not sure what all to calculate into the back pressure to size the poly (psi and diameter) and the pump.



What all do I add together?

300’ lift to head= 130psi

Does static level add any psi?

Pressure switch= 60psi

340ft run= psi?

CSV= 60psi?



Would a 5gpm 1hp with 300ft of 1” 250psi poly work? Or am I thinking about the math wrong and need something like 1-1/4” poly with 7gpm and switch to 3/4hp? I’d like to use a 2 wire pump to save on the copper going down and the simplicity of not needing a control box. Either way I should still be fine with the storage I’ll have in the well never running dry.



I guess once I know my total psi I can then look at the pump curves to know the answer to what I asked above.



With brands, are Grundfos and Goulds going to last the longest for the money? Or would a stainless Hallmark be a good choice too? Is there a clear winner in todays market for longevity?

 

[Reach4]

Would a 5gpm 1hp with 300ft of 1” 250psi poly work?

I think I have this right, but not sure.

With a CSV, see how much PSI the pump makes when pumping 1 gpm. Call that P1. That is the max the drop pipe deals with.

For the CSV, take the pressure head between the static water level and the altitude of the CSV (in PSI). Call that P2. Let's call the pressure cutoff at the pressure switch P3. That would be 60 PSI with your 40/60 pressure switch.

Pressure across the CSV would be P1-P2-P3. Max for that is 160 PSI.

Does static level add any psi?

So, yes.

 

[Sponsor]

 

[Valveman]

A 5 GPM, 1HP builds 560' of head. That is 242 PSI and is the max pressure the pipe will see. Take off the 155' to static from the 560' the pump can build, and you get 405', which is the same as 175 PSI, and also the back pressure at the CSV.

A 7GPM, 3/4HP only builds 400' max (173 PSI on the pipe), and 106 PSI back pressure at the CSV.