1. Fill a test tube (0608) to the 12.9 mL line with the sample water.
2. Add 6 drops of *Sodium Hydroxide with Metal Inhibitor (4259). Cap and swirl to mix.
3. Add one Calcium Hardness Indicator Tablet (T-5250). Cap and swirl until tablet disintegrates. Solution will turn red.
4. Fill Direct Reading Titrator (0382) with Hardness Reagent #7 (4487DR).
5. Insert the Titrator into the center hole of the test tube.
6. While gently swirling the tube, slowly press the plunger to titrate until the red color changes to clear blue.
7. Read the test results where the plunger meets the Titrator scale. Record as ppm Calcium Hardness as (CaCO3).

NOTE: If the plunger reaches the bottom line on the scale (200ppm) before the endpoint color change occurs, refill the Titrator and continue the titration. When recording the test result, be sure to include the value of the original amount of reagent dispensed (200ppm).