Which test is commonly used to measure hardness in water?

The soap test is commonly used to measure hardness in water because it provides a straightforward way to evaluate the presence of calcium and magnesium ions, which are the primary contributors to water hardness. In this test, a measured amount of soap is added to a water sample, and the amount of soap that lathers will indicate the hardness of the water. Hard water reacts poorly with soap, resulting in less lather formation compared to soft water. This makes the soap test an effective and practical method for evaluating hardness levels in various water sources.

While other tests like the pH test or conductivity test may provide insights into water quality, they do not specifically or directly measure hardness in the same intuitive manner as the soap test does. Chemical analysis can determine hardness as well, but it typically involves more complex procedures and equipment, making it less accessible for quick assessments. The soap test, therefore, stands out for its simplicity and effectiveness in measuring hardness.