We put a new 1/2 HP submersible pump in our well about 3 weeks ago. It worked fine for about 2 weeks, then it started surging while it's running. When the pressure drops and the pump starts you can here the water in the pipe surging until the pressure builds up and the pump stops.

Checked the current draw on the pump and it's steady at 5.75 amps, voltage at the well head is 240 volts.
There is about 70' of water above the pump in the well.
There is a pitless adaptor in the well and the line runs about 60' to the house and then about another 30' in the house to the pressure tank and pressure switch.
There is no leak at the pitless adaptor.
Pressure switch is set at 40 on 60 off psi.
Static pressure in the bladder tank is 36psi.
Well casing is 6".

The house is 38 years old and I suspect the old pump was original, never had a problem w/it until the check valve in the pump failed, so we decided to replace the whole pump instead of just the check valve. 100' of pipe is a lot to R&R.
TIA, Ken