1. Turn the unit on 2. Add water for testing 3. Only then press the ZERO button 4. Only then add the tablet 5. Be sure it is fully dissolved with the provided stirring stick. This could take up to 2 minutes 6. Cover the testing well 7. Only then press the appropriate testing button (e.g., fCl for Free Chlorine) By following these instructions, you will get accurate readings.
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