I am on well water, and have had problems in the past with excessive drawdown. A couple of years ago, I built a cistern system to remedy this. The outside submersible well pump (about 80 ft. underground) pumps into four 50-gallon barrels which are plumbed together, this is controlled by a float-switch in one of the barrels. Then, a shallow-well jet pump which is sitting right next to the barrels charges my 20 gallon pressure tank, and it on to the rest of the house from there. The jet pump is controlled by the original pressure switch, which is set to about 30/50. This has been working well for 2 years. Lately, I have been noticing that every now and then, the jet pump will be running constantly while the pressure in the system is stuck at around 35 or so. To fix it, I shut off the power to the pump, open a faucet until the pressure drops to around 15 or so, and then close the faucet and restore power to the pump. Then everything is back to normal. Any thoughts?

Is there a check valve between the jet pump and the bladder tank? Back to you, Tom