WHAT IS HARD WATER
Mineral deposits on dishes rings in tubs are not not signs of pore house keeping but of hard water.
Hard water is water that contains ions with a charge of t2 especially ca2+ and mg.
These ions do not pose a health risk, but they can engage in reactions that leave insoluble mineral deposits. These can make hard water unsuitable for many uses, and so a variety of mean have been developed to soften hard water,remove the the calcium and magnesium ions.