LaMotte DPC-52 Water Testing Laboratory - Manual (Page 16)

CALCIUM HARDNESS
Calcium Hardness is a scale forming element that will leave deposits on the side of a
pool at the air-water interface where evaporation takes place. Calcium deposits inside
pipes and fittings restrict flow and affect the heat exchange capacity of pool heaters.
Recommended levels in pool water for Calcium Hardness are from 175 - 400 ppm
Calcium Carbonate.
RANGE:
0 - 500 ppm as Calcium Carbonate (CaCO
3
)
METHOD:
Calcon is used as the indicator at pH 12 - 13. Calcon yields a
red color in the presence of calcium. The color changes to blue
when the calcium ions are sequestered by EDTA.
INTERFERENCE:
Excessive amounts of heavy metals can interfere.
DIRECT READING
TITRATOR METHOD:
Carefully read the User’s Guide for use of the Direct Reading
Titrator before performing the titration procedure described
below. The Titrator is calibrated in terms of Calcium Hardness
in parts per million Calcium Carbonate and each minor
division on the Titrator scale equals 10 ppm.
PROCEDURE
1. Fill the titration tube marked “HARD” (0645) to the line with the water sample to
be tested.
2. Add six drops of *Hard 1 Reagent (WL-4259) to the test sample. Cap and mix.
3. Add one Hard 2 Tablet (WL-T-5250). Cap and mix to dissolve the tablet. A red
color will appear if Calcium Hardness is present.
4. Fill Direct Reading Titrator (0383) with Hardness Titrant (WL-4487) and titrate the
test sample until red color changes through purple to blue. Read the test result
directly from the scale where the large ring on the Titrator meets the Titrator barrel.
Results are expressed as Calcium Hardness in ppm Calcium Carbonate.
CALCIUM HARDNESS ADJUSTMENT
In 10,000 gallons of water . . .
1 lb. Calcium Chloride increases Calcium Hardness 11 ppm.
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