Submersible pump

Got a call something is wrong with their water. Got there, pump was running but only had 20 pounds of pressure according to the guage. Installed new guage, showing the same thing, 20 pounds is all the pump is putting out. Checked double pole breaker, both legs showing 120 volts. Checked amperage draw, each side was drawing 6.8 amps. I tap on the tank, top is hollow, bottom kind of solid, checked air in tank, only 10 pounds. Filled to 28 pounds as it's a 30/50 pressure switch. Same thing. Would only go to 20 pounds. I checked the amperage draw at the casing, 6.8 amps each side. Pulled the pump, about 275 foot of pipe. Checked where top of water was at compared to casing and found water is only being lifted 25 feet to the pitiless adapter. Cut both wires at the pump and checked voltage on both sides, it had 120 on each leg. So I am thinking the pump or a few of the pumps stages are not working inside the pump. It had a 1/2 horse pump, replaced it with a 3_4. Still got the same problem. We noticed water at the casing on the ground, dug it up, found plastic fitting in pitiless adapter cracked. Also noticed there was only a foot of Polly pipe coming off the adapter then switched to pvc which runs directly beneath a massive oak tree. I figured maybe the pvc was cracked because of the root so we dug it up at the house and ran 1 inch Polly pipe above ground to bypass tree roots. Still have the same problem. Now I am thinking it may be the tank. But I have always seen the bladder rupture filling the tank with water, but never seen a bladder not let water in. Secondly I should have put an external check valve at the pump as when you cut the power off the water drains back. Also I only used a 3/4 pump because of only lifting water 25 feet. I was always taught that the water below the top of the water in the well don't count as weight.

Any thoughts?

Via RSSMix.com Mix ID 8247361 http://www.rssmix.com/