Water hardness tester with a bottle, liquid, and a small measuring test tube.

Instructions for use:

• Fill the test tube up to 5ml with the water you want to measure.
• Then add the liquid drop by drop into the water until it changes from red to green. Once the water turns green, stop adding drops of liquid.
• The number of drops you added corresponds to the German degrees of hardness of your water. For example, if you add ten drops until the water turns green, then you have ten German degrees of hardness. The tester has a deviation of one unit. That is, if you add ten drops, then the hardness is ten degrees plus or minus one degree. Initially, the water may turn red. However, you should continue until it turns green. 

After measuring the German degrees with the hardness tester, refer to the following list to see how hard your water is characterized:

• 0-4 German degrees: Very soft
• 4-8 German degrees: Soft
• 8-12 German degrees: Moderately hard
• 12-18 German degrees: Fairly hard
• 18-30 German degrees: Hard
• >30 German degrees: Very hard