To stop tearing your hair out, go buy a gallon of distilled water from the grocery store. Rinse the TDS meter really well with some of it. Also clean the hell out of a glass with it. No soap. Then measure a sample of the distilled water and see what the TDS reading is. Not perfect since you would usually want to calibrate with a lab grade reference sample to some known TDS value like 50 or 100, but using distilled and adjusting the meter to read 0 is also ok.Hell if I know it came with my zero water filter for drinking inside
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