LLigetfa
DIYer, not in the trades
I figured it would be easy enough to ascertain simply by pulling up the drop pipe. Personally, I would have done that before digging up the yard. The buried stuff can simply be pressure tested and if it isn't metal pipe it doesn't need to be inspected for corrosion.
Curiosity alone WRT that second pipe would be enough for me to open the well and if there were a suction side leak, I would test the drop pipe first. The mystery of the presumed second checkvalve would also compel me to open the well.
Also, since you feel the need to have filters in-line, I would be curious about the condition of the well WRT silting in and would be making plans to purge it. Purging/surging could also increase the yeild.
Curiosity alone WRT that second pipe would be enough for me to open the well and if there were a suction side leak, I would test the drop pipe first. The mystery of the presumed second checkvalve would also compel me to open the well.
Also, since you feel the need to have filters in-line, I would be curious about the condition of the well WRT silting in and would be making plans to purge it. Purging/surging could also increase the yeild.