Test Method
1) Select the sample size appropriate to the hardness range under test. Take a sample of the
correct size in the sample container.
2) Add one Total Hardness tablet and shake the container until the tablet disintegrates.
3) Continue adding tablets one at a time in this manner until the colour of the solution
changes from plum red to blue.
4) Note the number of tablets used and calculate the result from the formula below
appropriate to the sample volume taken.
Total Hardness Calculation
Sample Size Total Hardness mg/l CaCO3
200 ml = (No. of Tablets x 10) - 5
100 ml = (No. of Tablets x 20) - 10
50 ml = (No. of Tablets x 40) - 20
Cleaning
Thoroughly rinse out sample container after use.
Note
1. This test measures total hardness, i.e. the total content of calcium and magnesium ions in
the water.
2. The expression of hardness results is normally expressed as mg/l CaCO3 (calcium
carbonate). This is a convention to allow the comparison of different results and does not
necessarily indicate that the hardness is present in the water in only the calcium form.