How do you measure the hardness of water?

To measure the hardness of water, either titrate a sample of the water with an ethylenediaminetetraacetic acid, or EDTA, solution or use a test strip kit. Hardness refers to the amount of minerals in the water, such as calcium, magnesium and iron. When soap is added to the water, it binds to the minerals and forms a solid.

Use the following steps to measure the hardness of water:

1. Gather the materials

Gather together the materials needed to test the water, such as a titration kit or test strip kit. Test strips are useful when only a general range is needed. When the specific level of hardness is required, use a titration kit.

2. Take a water sample

Place a sample of the water being tested in a container to make it easier to add the titration solution.

3. Add the solution

Take a dropper and add small amount of the titration solution to the water sample until it begins to change color. If using a test strip, add the strip to the water sample and allow it to change color.

4. Compare to the chart

Compare the color to the chart provided by the kit. Hardness is typically measured in milligrams per liter as CaCO₃. Water that has a reading of 17 mg/L or more is considered to have some level of hardness.