hardness vs pH: [link] “Hard water (high mineral content) is usually high in pH. Soft water (low mineral) is usually low in pH.”

is soap better than detergent? [link] “If you live in an area where the water is soft, you will have more success with soaps, but even then a gradual build-up of calcium and magnesium ions (also called ‘curd’) will be left in the fabric of your diapers”

here is a picture: [link] “When soap is added to hard water, insoluble compounds form which appear as sticky scum.”