[OGD] pH of RO Water

[Martin Epstein]

Olga, don't sweat it.  For orchid growing purposes the pH of RO water 
is meaningless.  RO water is not buffered, that is it varies with 
only minor compositional changes.  It reflects traces of 
acidity/alkalinity and is due virtually entirely to dissolved carbon 
dioxide.  The various ions available from your potting medium will 
swamp whatever value you measure.

Of much more importance is the pH of your fertilizer solution; that 
is buffered.

Martin

At 6:43 PM +0200 8/12/04, Olga Caussade wrote:
Many thanks to Nick, Paul and Peter for your answers.
For Nick,  I have RO water and it has a pH of 6.5 before storage.
For Paul, no my pH meter do not have a temperature compensation function.
For Peter, I do not have any plants or algae in my water.
The problem is that I grow Phrags and I try to do it between a pH of 5.5 to 6
and this fluctuation give me much more work to calibrate my water.
Does pollution and heat could provoque  wholly or partly of this difference?
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