Sizing your Submersible Pump for "Old" or "New" well

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Sizing your Submersible Pump for "Old" or "New" well

Postby Pumpmd » Tue Mar 07, 2017 1:22 pm

For future reference when pulling your submersible well pump or "New" well drilled.



What are your well specs? How deep is it to water and your total depth of the well. Things that could've been checked very easily, when the pump was out of the well.

How much water does your well produce? You don't want to pump it off during long term water use without, having a safety device(I use Pumptec on Franklin motors).

What size was the motor(HP)and what size was your pump end(gpm)?

What size is your pressure tank(gallons) and the "Brand"? Do you perform "Preventive Maintenance" on your pressure tank?

Our oldest Goulds pump that I've found installed by my grandpa, was almost 48yrs old. It came from a farm with alot of "starts" from a 82gal standard tank. I have pictures and the old paper file from the job to show.



For New wells, the well driller will tell you where the bottom "perf" is, in your well. Don't set your pump below that because your well isn't going to produce anymore water below that point and you want the best cooling for your submersible pump. You want the water to flow past the motor and through the pump. 20-40' above the bottom perf is what you want. You "only" set the pump below the bottom "perf" if you need it for water "storage" because you have a weak producing well(Pumptec). Not all well drillers can keep abrasives out of your well and why you don't want the pump set to close to the bottom of your well.
Last edited by Pumpmd on Tue Mar 07, 2017 2:52 pm, edited 1 time in total.
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Re: Sizing your Submersible Pump for "Old" or "New" well

Postby Pumpmd » Tue Mar 07, 2017 2:49 pm

What are your needs (gpm) flow rates. Everything has a gallon per minute flow rate. When sizing your sprinkler system, you size it to the pump. If have a 20gpm pump, you use 18-20gpm on each zone (you want to keep the pump running but, it can still build around 50psi). Your pressure switch is going to be 40-60, so anything under 60psi. Your pre-charge inside your pressure tank will be 38psi(check every 6-12 months). The extra "gpm" is going to be for water use inside your house. If, you use water while the sprinkler system is running.

Remember this "The larger the pipe, the less the friction loss, the greater the volume, the better the pressure". Our job stops at the house valve.

"water savers" used to save water for people on city water that has higher water pressure than someone on a traditional well system(goodbye water saver aka "flow restrictor").
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Re: Sizing your Submersible Pump for "Old" or "New" well

Postby Pumpmd » Tue Mar 07, 2017 9:41 pm

Pressure Tank Sizing

4in motors require 1min on and 1min off, for proper cooling.

6in and larger motors require 15min on and 15min off, for proper cooling.

Depending on your depth to water (static water level) and your "gpm" pump end, is how you size your pressure tank. Pressure tank's have a drawdown in "gallons", the drawdown will change on different psi setting (20-40,30-50,40-60), so keep that in mind for proper cooling.
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