I am in the process of trying to determine the cause of extremely low water pressure and flow rate from my well. The well has a submersible pump (3/4 hp I believe from what I read on the control unit). The pump was working fine then during a week or so the pressure dropped significantly. I'm not completely sure the actual time it took for the decrease in pressure to result due to there was no one consistently in the house. The pressure gauge off the control unit reads around 9psi static pressure and then hovers around 4-5psi with water flowing. The flow rate directly at the water tank is approximately 2.5 gal/min. There is a water softener, but I've checked to see if that was the problem by bypassing the system (also where I checked the flow rate is before the water softener). I believe the water tank itself is all right. I turned off the well pump, drained the system and then checked the pressure in the bladder, which read 28.5psi.

I feel its either the control unit not sending enough power down to the system or turning off prematurely. Or the well pump is limping along not working nearly at full capacity. I don't know how old the well pump or control unit it, we only bought the house with the past couple of years. Not quite sure how deep the well is either, the neighbor's is just over 500ft so I could image that would be quite a bit of piping to pull out if necessary.

Please help, I'd rather not pull up the well pump only to find out it was the control unit.

MIGHT be a switch problem. Your pump should pump up to 50# or so (depends on what the switch is set to), at which point the contact points in the switch separate and the pump stops. Once pressure falls to 30# (or whatever the setting is), the contact points come back together and the pump turns back on. If your pressure is at 9#, then something is obviously wrong. Take the cover off the switch and look at the points to see if they are closed. If they are closed, then is the pump running? IF they are not closed at 9#, then either the switch is bad or the little small tube that connects the switch to the system is clogged and not allowing the switch to "sense" pressure.

I checked the control unit again. You can hear the control unit click to come on after the power was turned off, but it does not click to turn power off. It seems as if it just remains on continuously. Does this mean power is constantly being sent to the pump, but the pump is just not able to reach to correct pressures? In which case the pump itself needs to be replaced?

If you have the power off, the switch will not click the second time because the pump will not be running and will thus not pump up to the cut off pressure. Your switch should have a grey cover held on by a single nut. Remove the nut, take off the cover, and watch the switch as discussed above. You can turn off the power to remove the cover, but the power will have to be on to watch the contact points open/shut as they should. That is not a problem so long as you don't touch the switch.

This site has excellent pictures and a good description of the operation of the switch.

How to adjust water pump pressure, pump cut-on pressure and pump cut-off pressure - private pump and well system do-it-yourself repairs