Steve has a good point that dissolved impurities can contribute to discoloration. Stan even says
this in the Environmental Tape The well water in southern Ohio
often has a high iron content but if you were to run a demo unit with for first time with distilled
water you still get discoloration form the slight corrosion of the non stainless bolts that Stan used as well
as corrosion if the stainless. The demo units I made used all stainless bolts or nylon (r) bolts, and when operated
with water they still became discolored but more so the longer and more times one operated the unit
without changing the waiter but just replenishing the water to keep the water level above the top of
the stainless tubes
