Bill,

Typically, as D.I. beds begin to fail (exhaust) either the cation or anion
(as a function of your H2O constituents) exhausts first which causes a pH
imbalance.  This occurs increasingly below approx 500K, so 1M builds in a
margin of safety that the water quality will be within reasonable
boundaries.

If you want to confirm this, simply measure the pH (inexpensive pocket
meters are available from Fischer Scientific) as yor beds fall below 1M and
plot the curve pH vs. resistivity.

Hope this helps!

Regards,



Ed Popielarski
QTA Machine
10 Mc Laren, Suite D
Irvine, Ca. USA 92618
Ph: (949)581-6601
Fx: (949)581-2448
E-Mail: [log in to unmask]

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