Help! Is our submersible pump ruined?

[LLigetfa]

There is a 3/4" spigot on a post next to the well, with a 100lb pressure release valve above the hose connect (in case the hose gets shut off). We connect a hose to this spigot and turn the well on and off at the breaker. We normally get about 5GMP out of the well.

I just checked, and the pump is actually 400' down, not 300'.

I think somebody failed at math. I doubt that pump can produce 100 PSI if the water level drops anywhere near 400 feet so that PRV will not save the pump from deadheading. A pump should not be set below its deadhead level without a good pumpsaver or cycle sensor to protect it.

 

[George G]

@Fitter30
The well is 600' deep. The static level is usually about 30-40' down.

 

[Sponsor]

 

[George G]

I think somebody failed at math. I doubt that pump can produce 100 PSI if the water level drops anywhere near 400 feet so that PRV will not save the pump from deadheading. A pump should not be set below its deadhead level without a good pumpsaver or cycle sensor to protect it.

The well driller set the system up, so all calculations (right or wrong) were his.

 

[George G]

Clip the amp meter around one of the hot wires at the breaker, pressure switch, or control box. When the pump starts and there is plenty of water in the well a 3/4HP should draw about 7 amps. As the water level drops in the well the amps will decrease and probably drop to about 5-6 amps when pumping 5 GPM. But if you pump the well dry you will see the amps drop suddenly from 5-7 amps to 2-3 amps. That means your pumping the well dry. If the amps start out low and you are sure there is plenty of water in the well, the pump could be worn or the screen clogged. If the amps ever go above 7 amps, the overload should trip and turn off the motor, showing zero amps. If starting the pump causes high amps and trips the overload, the start capacitor in the motor or control box is bad.

@Valveman

So, I tests for amps yesterday. At startup with the well fully recharged and running wide open it pulled about 8.2 amps.
Once I switched the 3 way valve to feed the garden hose and spray nozzle it dropped down to about 7.7 amps. It ran normally, no issues, no loss in pressure, and the amps were steady for the entire duration of usage, about an hour.

 

[Valveman]

@Valveman

So, I tests for amps yesterday. At startup with the well fully recharged and running wide open it pulled about 8.2 amps.
Once I switched the 3 way valve to feed the garden hose and spray nozzle it dropped down to about 7.7 amps. It ran normally, no issues, no loss in pressure, and the amps were steady for the entire duration of usage, about an hour.

Sounds like everything is OK to me.

 

[2stupid2fixit]

not only just OK, I think those numbers are healthy. others will tell me that this is a bad suggestion but, it helps with calculations because you can see what your well can actually DO.

1, Open a port on your wells supply that goes only from the pump output to nothing else, except a pitless adapter. first stop on the line, open it up.

2. Bring a snack, and make the well pump run until it clearly has run out of water. If this experiment goes longer than 2 hours, stop trying to use your submersible pump to empty a lake or river. You won't run dry.

3. If your pump sputters air or stops pumping water, the time between your start and when you ran out of water or saw air spray tells you about your well recovery rate.

 

[George G]

Sounds like everything is OK to me.

Thanks a lot for your help!

 

[George G]

not only just OK, I think those numbers are healthy. others will tell me that this is a bad suggestion but, it helps with calculations because you can see what your well can actually DO.

1, Open a port on your wells supply that goes only from the pump output to nothing else, except a pitless adapter. first stop on the line, open it up.

2. Bring a snack, and make the well pump run until it clearly has run out of water. If this experiment goes longer than 2 hours, stop trying to use your submersible pump to empty a lake or river. You won't run dry.

3. If your pump sputters air or stops pumping water, the time between your start and when you ran out of water or saw air spray tells you about your well recovery rate.

We have done this a few times. Shortly after drilling the well we could run it for about 2.5 hours before it ran "dry".

A few months later, we tried again and were able to run the well for over 5 hours and never ran it dry, so clearly it started producing a lot more water than ever before. Since then we haven't bothered trying to run it down, although it sounds like we may have inadvertently done so the other day...

All in all we're just relieved the pump seems to be acting normally. Thanks all for your help!

 

[JohnnyVirgil]

A 3/4 hp 5 gpm pump is enough pump. It has more stages, and it can raise water higher.

A 3/4 hp 7 gpm pump is maybe enough pump, and that could explain your symptom-- as the water level approached 300 ft down, the flow rate would reduce. That is not all bad when you contrast that with sucking air.

A 3/4 hp 10 gpm pump is not enough pump to produce pressure for running a garden hose nozel sprayer , and that could explain your symptom-- as the water level approached 300 ft down, the flow would reduce considerably. That is not all bad when you contrast that with the alternative of sucking air.

I'm confused by this. Isn't 10 gallons per minute better/more than 5 gpm?

 

[Reach4]

I'm confused by this. Isn't 10 gallons per minute better/more than 5 gpm?

Depending on the job, but generally no. A 5 gpm submersible well pump will have more stages, and will be able to provide the pressure to climb higher. It will be more expensive. When you see pumps that are just rated for HP and gpm, those are usually 10 gpm or more. And they cannot develop as much pressure as a 7 gpm or 5 gpm pump for a given HP.

Not a great analogy, but consider bicycles. If you get one rotation of the drive wheel for each turn of the peddles, we would have a 1:1 ratio. That might be low gear. If we had 4 wheel rotations per turn of the peddles, that would be 4:1. Which is better? Depends on the job. Traveling on a smooth level road, 4:1 is great. For steep uphill roads, 1:1 is better. With a bicycle, the conditions change. So a gear shift method is good. For a pump, they don't do that. So you pick one that will do the job over the range of conditions.

So what does a "10 gpm" pump mean? For quality pumps, that is the point on the flow curve where they are most electricity-efficient. For some cheap, in the worst sense, pumps, it is the flow with zero backpressure (a rise of 0 ft).

 

[JohnnyVirgil]

Ah so it has to factor in the vertical lift capability before those stats actually mean something.