A water spot is an area of dried mineral

Mineral

A mineral is a naturally occurring solid chemical substance formed through biogeochemical processes, having characteristic chemical composition, highly ordered atomic structure, and specific physical properties. By comparison, a rock is an aggregate of minerals and/or mineraloids and does not...

 deposits left on a surface after being allowed to air dry. Water quality

Water quality

Water quality is the physical, chemical and biological characteristics of water. It is a measure of the condition of water relative to the requirements of one or more biotic species and or to any human need or purpose. It is most frequently used by reference to a set of standards against which...

, specifically the amount and type of minerals in the local water supply as measured by the total suspended solids

Total suspended solids

Total suspended solids is a water quality measurement usually abbreviated TSS. It is listed as a conventional pollutant in the U.S. Clean Water Act. This parameter was at one time called non-filterable residue , a term that refers to the identical measurement: the dry-weight of particles trapped...

 or TSS test and other mineral levels such as sodium

Sodium

Sodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is 23Na. It is an abundant element that exists in numerous minerals, most commonly as sodium chloride...

 level, has a big effect on how severe water spots can be, for example on an automobile or dishes. Water spots can be avoided by drying after washing, using a "shammy" cloth or towel for a car and a good drying cycle in a dishwasher

Dishwasher

A dishwasher is a mechanical device for cleaning dishes and eating utensils. Dishwashers can be found in restaurants and private homes.Unlike manual dishwashing, which relies largely on physical scrubbing to remove soiling, the mechanical dishwasher cleans by spraying hot water, typically between ...

, or by manual drying or good drainage after manually washing dishes.

For permeable materials, such as a drywall

Drywall

Drywall, also known as plasterboard, wallboard or gypsum board is a panel made of gypsum plaster pressed between two thick sheets of paper...

 ceiling

Ceiling

A ceiling is an overhead interior surface that covers the upper limit of a room. It is generally not a structural element, but a finished surface concealing the underside of the floor or roof structure above....

, water spots or stains are permanent indicators of water damage

Water damage

Water damage describes a large number of possible losses caused by water intruding where it will enable attack of a material or system by destructive processes such as rotting of wood, growth, rusting of steel, de-laminating of materials such as plywood , and many, many others.The damage may be...

and previous leaks.