Check out my 2018 update of this video, with far better sound quality: Using Soap to Test for Hard Water.
The term “hard water” refers to the concentration of minerals dissolved in the water. “Soft water” indicates that there are very few minerals in the water. In this video, I demonstrate how to test for it in your water supply. You can then use this information as a tool to diagnose issues around your house, such as why soaps don’t rinse as easily, why you have soap scum, why there’s build up of mineral deposits inside faucets, and why you may have lower water pressure due to build up in pipes. Keep in mind, from my soap scum blog, that acids (like vinegar) dissolve water deposits.