Rough Calculations for Pumping a Deep Well

[stubbornrussian]

So I have been thrown a question about pumping an underground water supply which is a little outside of my comfort zone. A friend of a friend has a piece of land with a sizable underground water supply. A 36 inch diameter cased well and 24 inch monitoring well have both been drilled and the well will be pulling from around a thousand feet deep. If I wanted a rough estimate on the cost in energy to pump a certain amount of water from the well what kind of specifics would I need assuming I was using a typical pump for such an application. And what type of pumps are generally used for pulling water from such a deep well. Thanks in advance.

Tim

 

[BigInch]

Hw_ft = Distance from the lowest well water level to surface
Hu_ft = required user_head_ft = required_system_pressure_psig * 2.31

Total_pump_head Ht = Hw + Hu

Pump discharge pressure_psig = Ht / 2.31

The required hydraulic power is,
Power_ftlbs_per_sec = Ht * Q_gpm /7.4805/60

Q_gpm = flowrate in gallons per minute

HorsePower = Power_ftlbs_per_sec /550
Power_input_to_pump (Hp)= HorsePower/Pump_Efficiency

For rough estimate use a pump efficiency of 0.65 or have a look at a manufacturer's catalogue.


Electrical Power required is,
Power_input_to_motor (kW) = 0.746 * Power_input_to_pump / motor_efficiency

Say 0.9 for motor efficiency.

multiply your power input to motor by the cost per kWh x the running time.

Use a submersible pump, typical fig here,

http://www.ag.ndsu.edu/pubs/ageng/irrigate/ae1057-8.gif

Goulds Pumps residential water supply website,

http://www.goulds.com/master.asp?ID=3#2

Grundflo also makes many different water well supply pumps.

University of Nebraska irrigation website,

http://www.ag.ndsu.edu/pubs/ageng/irrigate/ae1057w.htm#Submersible

Let us know if you need mo info.


BigInch-born in the trenches.

http://virtualpipeline.spaces.msn.com

 

[stubbornrussian]

Thanks so much, I'm looking it over now and it seems pretty straight forward. I still cant find a pump to fit those dimensions though. Are pumps of such size even made. The largest that I can find so far is a 10 inch pump.

 

[Artisi]

What size pump do you need? - pump sizing will depend on required flow and head.

Head will be the vertical height from the expected pumping drawdown level to the highest point of your discharge pipe work plus all friction losses in the rising maim and delivery pipe work.

For interest - what is the flow rate you require and what

A thousand foor deep well doesn't give any indication as to what the standing water level is and what the pumping level is - without this information you are guessing

 

[Artisi]

Correction to the last post;

For interest- what is the flow rate you require and what is the anticipated head?

 

[BigInch]

The pump and riser pipe don't need to be 36". The pump can be suspended from a smaller diameter riser pipe. The riser pipe can have guides keep it from moving within the 36" casing. The size of both pump and riser pipe depends on the flowrate you will need. Pump pressure rating depends on the total head. What is the required flowrate (gpm) and total head (feet)?

BigInch-born in the trenches.

http://virtualpipeline.spaces.msn.com

 

[thewellguy]

I'm wondering where is the world your site is? A 1000' residential well is not common in the mid west. At least non of the size. A typical residential well has a bottom diameter or 5" or 6." The well size you mentioned is usually reserved for cities, and large industry, not residential.

As far as pumps go, a 4" diameter pump is the standard for a residential application and there are many manufacturers. Goulds, Berkley, sta-rite, Grundfos, Mcdonald, just to name a few. Please provide more info on you pumping conditions and available power supply and I will be happy to help you find a pump that will fit.

 

[RossABQ]

I had a 1050 ft residential well (serving 3 homes ultimately) in the Albuquerque area. Water level was over 980 ft down. It had a 5 HP submersible multistage pump (3 bowls as I recall). A key factor on submersibles is that the wire size required for a given HP takes a jump at several depths/lengths, and at 1,000 ft it cost me another $500 for the next size wire, which in turn drove a larger well casing (8" as I recall) just to accomodate all the wire and pipe.

Based on the sizes of the casings quoted, I'd guess this is a large irrigation well.

 

[thewellguy]

RossABQ, you are correct. I didn't have enough coffe yet. In many cases like your where ther is only 230 1 phase power available, the wire ends up costing more that the pump and motor.