Submersible pump choice help

[Limicolous]

Hi,

Thank you for all the help before. As our Jet pump seems to be slowly biting the dust, I was hoping I could get some advice on submersible pump sizing.

See if this head pressure calculation makes any sense to you. This is off of the internet.

Max water pressure required - 60 (With a 60-40 pressure switch) pressure required x 2.31 = 138.6'

Depth of pump location (regardless of water level, 75' well) = 55'

Stories of the house (I was a little confused by this as our house will be two stories when finished but the well is also at basement level) for current use say 2 x 10' = 20'

Distance from well to pressure tank, 25' (125' 1" pipe = 6 feet of head pressure) = 1.2'

Total maximum head pressure needed, 138.6' + 55' + 20' + 1.2' = 214.8'
__________________________________________________ ____________

Looking at the Goulds 1/2 HP 10gpm pump curve, it tops out at about 210' of total dynamic head. While the 1/2 Hp 7gpm or the 3/4 hp 10 gpm don't seem to be very efficient in the lower psi between 40 - 60 psi and 25 - 40 feet of water depth, at which the pump will probably be operating the most. (10gs is the 10gpm pump and 7gs is the 7gpm model)

What should we do? Does one generally try to over size a little bit on your pump, or is this just a waste of money?

If I under size will I have bad water pressure and risk burning out the pump?

Will a CSV maintain the head pressure so that a larger pump can work efficiently at a lower work level? We have a large 75 gal. pressure tank so would a CSV even be helpful?

Thanks for your expertise and time.

Elizabeth

[Porky]

Since you don't know what the well produces I'd stay with a 1/2 hp submersible pump. A Goulds is a good pump and will give you plenty of pressure. A CSV will give you a constant pressure (you'll love that when taking a shower). I suggest that you call Cycle Stop Valves @ 806-885-4445 and anyone there will be happy to walk you through everything.

[valveman]

You can use as large a pump as you want, and the CSV will make it work like a small pump when a small pump is all you need. Even if your well only makes 7 GPM, you can use a 10 GPM pump, just don’t open more than 7 GPM for extended periods of time. But with a 10 GPM pump, you can use 10+ GPM for short periods of time, until the well pulls down. This will give you better pressure for things like multiple showers going on at the same time. You just have to shut the showers down before the well pulls down, if the pump can put out more than the well can produce.

[Limicolous]

Thanks guys.