Is using distilled water to mix my calibration powder a major no no?

[growsomebuds]

The instructions for my new pH pen instructs me to mix the calibration powders w/ deionized water. That stuff is crazy expensive. Do I absolutely need to use deionized water or can I get away with distilled water?

[Toker1]

It’s not the same thing. I would follow the manufacturers recommendations.
Distilled is water vapors caught and condensed. It removes most impurities but some are vaporized along with the h2o and condensed as well.
DI water is run through a cation then anion bed. Or a mixed bed. It removes any particle with a positive or negative charge.
DI water will be closer to pure H2O than distilled.

[Farmall]

Depending on the distillation process, the chemical elements in the make up of the kettle and tubing will change ph of the water.. example.... many decade Ago we were experimenting with marine aquariums and instant salt. The base water had a extremely high copper ion concentration as the still was made with copper tubing. Being an invertebrate fish tank, they would have all died within 24 hours or less and copper is highly toxic to marine invertebrates ...unless you know the process used or can test for metals....be cautious

[growsomebuds]

Depending on the distillation process, the chemical elements in the make up of the kettle and tubing will change ph of the water.. example.... many decade Ago we were experimenting with marine aquariums and instant salt. The base water had a extremely high copper ion concentration as the still was made with copper tubing. Being an invertebrate fish tank, they would have all died within 24 hours or less and copper is highly toxic to marine invertebrates ...unless you know the process used or can test for metals....be cautious

I can measure TDS and EC. Would that help to see if distilled water is doable?

[Farmall]

I had only discovered this because copper testing is normal for saltwater aquariums. When the copper went off the charts, I re-tested and then realized the issue. I don't know how you can tell unless the company selling the water can advise you