rusty water, then clear, repeat

[showghost]

Our well was drilled 5 years ago 280 ft, 80-gpm. When we turn the hydrant on it runs brown-yellowish so bad I can't see through the water in a glass, then it clears right up and runs and tastes great. Let it sit for a while, turn it back on and it does the same thing again. There's not much consistency in how long it takes to turn brown again. some times the same day, some times the next day. We let a glass sit out and it did not clear up overnight, what I've read is that we have colloidal iron. We do not have iron bacteria, the water doesn't smell for leave slime. We have an iron casing with a galvanized pipe to the pump. Is it true the pipe could be rusting this early (5 years old)? The well driller has suggested lining the well with PVC? We did try shocking once and it cleared up for a few weeks but is back to doing the same thing again. Our neighbors well (100 yards away) is 240 ft, metal casing, 25 years old, no problems. Any suggestions out there...