Well Pump FLow Rate

Factual Questions
1

What average flow rate (gpm) should one expect from a well pump for a residential application? IIRC, 3 gpm sticks in my head. But, I forget if this is the flow rate expected from the well pump…or the flow rare expected at the faucet.
(Note: My well pump is designed to fill the “air tank”. The air tank then supplies the water, at the correct water pressure, to the house.)

Is it 3 gpm for both? If not, please be specific when quoting a flow rate in your reply.

Thanks,

  • Jinx
2

A quick look at the specs in a Grainger catalog for shallow well jet pumps puts the low end at ~3 GPM when 25’ lift and 40-50 PSIG is requested. Lower lift and less pressure raises the GPM up to almost 30 for some models. Some deep well pumps deliver better than 3 GPM @ 260’ lift. Submersible pumps range from 5 to 85 GPM, again ranging from depth, and also well capacity. A high output pump in a low capacity well will “overpump” the well and shorten it’s own life.

3

Thanks for your help, but this is all well and good for pump selection. You can buy a pump to deliver any flow at any pressure. What I want to know is what the end user can expect in performance from an existing pump.

Regardless of set-up, a residence should expect x gpm from a well pump. For example, my pump is 500 feet deep, so more pressure is req’d (suction head) to lift the water, and a bigger motor, etc…

But, the question remains, what flow rate is the target for residential? (Heck, a builder ain’t gonna put in a Cadillac of a pump when s/he can get away with less!)

  • Jinx :confused:
4

Three gallons per minute is a reasonable flow rate for a faucet. Low flow shower heads typically are rated at something like 2.5 gpm. Residential water pressures vary widely but typically run between 35 psi and 70 psi. But that isn’t what your well pump has to do. Your well pump just has to deliver enough pressure to lift the water into your storage tank, eh?

5

You will need the pump performance curve for that particular pump. If you know the vertical lift, motor speed, and tank pressure (and maybe add 1 or 2 psi for friction losses, depending on the amount of pipe between the pump and tank), you should be able to determine the flow rate. The problem there is getting the pump curve if you don’t already have it. Maybe the manufacturer has it online, or whoever drilled your well has it.

I’m on city water, but I’m able to get 5 gpm out of a 1/2" hose bib. At that rate, I have no problems. I think 3 gpm would be a little low but I could live with it. I wouldn’t want to go much lower though.