> Ellen York asked about changes in water quality with RO, and Wayne
> Forester replied that RO water is not corrosive. The contrary is
> true. RO removes most of the bicarbonates and leaves the CO2 in the
> water.This causes a lowering of the pH (values around 4 are possible)
> so this water will eat through the metal pipework.
John,
This must depend on the water you start with. The RO waters I've
worked with have all been only slightly acidic, pH ~6.5. Also, the
original question said that distilled water was more corrosive.
Generally, the pH of pure water should be neutral. I'm not sure of the
source of carbon dioxide you refer to, but I assume it's not atmospheric,
because gases relatively quickly equilibrate with water, and would
reach equilibrium. I have not seen significant drops in pH of RO
water that has then been purified by MilliQ filtration. Perhpas you could
clarify this for me. Thanks,
Wayne Forrester