You'd be suprised how fast well water absorbs O2 from the air.
Brian, you have a meter. Can you run well water into a bucket and keep the end of the hose submerged in the water and test the O2 levels, then do the same thing except keep the end of the hose out of the bucket by about 3'-4' and test the O2 level again once the bucket refills? I'll bet the difference in O2 levels will suprise DD1.
