I was wondering about the sensitivity of the probe being near the dispenser. Without very sensitive adjustments it would seem that you could easily overdose the resevoire if the current pulled the concentration away from the probe.

As a thought, how about putting the probe inside a cup with the dispenser tube in the cup as well (cup inside resevoire)....that way a small dose would immediately trigger the shut-off. The cup of high ph would then drift into the resevoire at a slower pace without having to dillute the solution.

GM