A common problem we see in high use public washrooms and commercial washrooms are the build up of hard water and soap scum build up around the faucets and sink. Once the minerals and cleaning products penetrate into the stone and harden they are very difficult to remove. Often requiring the surface to be sanded and re-polished. We recently completed a project in a commercial building doing just this.
Problems Caused by Hard Water:
"Hard Water", is water that has a high concentration of dissolved minerals (usually magnesium and calcium). Water is foremost a solvent (carrier). It picks up impurities easily. The degree of water hardness increases with increased levels of calcium, magnesium, other minerals and trace elements.
Hard water is not bad for you at all, however it's a pain when these minerals cause stains and contribute to other cleaning problems. Water stains are usually white in colour, but they can also be brown or rust colored when iron or other trace elements are present. When standing water is allowed to naturally evaporate away, the minerals are left behind and form a hard and hazy looking stain.
If hard water deposits are not addressed, the minerals in the water can permeate stone surfaces making it very, if not extremely difficult to remove.
The minerals in water don't just cause stains; they interfere with cleaning products, detergents and soap resulting in less effective cleaners. Because of the reduced cleaning power, hard water also causes more soap scum, sediment and debris to form in areas where water is used. (Showers, kitchen counters, vanities, etc.)
The additional sediment build up then can cause further soap scum and mold and mildew to form.
Frequent cleaning and regularly re-sealing the stone will help prevent this from happening.