Using AC unit run-off water with low pH and TDS

[Dumb chemist]

I guess I should add my 2 cents worth to this discussion:

The pH meters I have used in the lab have always been the ones with an analog or digital readout and with a pH probe and an Automatic Temperature correction probe (ATC). The meters were always calibrated with standardized pH calibration solutions. The meters were calibrated daily to ensue accuracy. Unless the pocket pH meters are calibrated just before use, I would wonder about their accuracy. pH test paper is accurate to a full pH. There maybe test papers that can go to a half a pH unit; but, I have not seen any. I would use the pH test paper first.

The use of A/C condensate water on Orchids is not a good practice IMHO. The condensate is in contact with the condenser coils before it enters the collection bucket. The coils are made of (pregnant pause) METAL. The metal is usually stainless steel which is made of iron and chromium. The water will pickup iron and chromium ions during its brief contact with the coils. What I would say is this: Would you drink the A/C condensate? If the condensate is not potable, would you use it on your Orchids?

Chemist joke:
Did you know that they found the universal solvent? The only problem is that they could not find a vessel to store it in.