Water can vary immensly
Natural Mineral Water
A product of pristine purity. By law, natural mineral water must originate from a subterranean source that is protected from every possible contamination. Only water that has been officially approved and tested for purity may be dubbed "natural mineral water". Before reaching this stage, it must pass about 200 separate analyses.
In order to retain the certified purity until the time of consumption, mineral water must furthermore be bottled directly at its place of origin – filled straight into the containers meant for the consumer.
As already indicated by the name, mineral water not only supplies water to the body but minerals as well - in varying amounts and proportions, depending on where it originates from. Like vitamins, minerals are essential to the body. Every day they need to be part of the diet in sufficient amounts, since the human body cannot produce them on its own.
Chemical agents, additional minerals or other types of water may not be added to natural mineral water. Solely the removal of iron (de-ironing) or sulfur is allowed. Iron might form residue in the shape of unaesthetic brown flakes at the bottom of the bottle. Too much sulfur would smell and taste.
The adjustment of the amount of carbonic acid contained is admissible. Carbonic acid as such is thus not a typical characteristic of mineral water. The purity and naturalness of every mineral water is monitored through regular analyses. As soon as even the most minor of contaminations is detected, the water loses its attribute as "natural mineral water" and may no longer be so called.
Natural Health Water
"Natural health water" stems from special mineral springs and is subject to the strict guidelines of the German pharmaceutical law. Belonging to the so-called ready medicines (Ger. Fertigarzneimittel), health waters must offer some kind of medicinal potency, for instance by guarding against or alleviating certain illnesses, or even curing them. The medicinal effect is proven through an elaborate procedure and only then approved by the law.
St.Gero Heilwasser is such a natural health water. It is for instance applicable in cases of gastro-intestinal diseases, various aliments of the kidneys and osteoporosis. But healthy people can also benefit from the excellent quality and the favorable composition of a health water such as St.Gero, and may drink it without constraint just like any other mineral water as a thirst quencher.
Spring water stems from subterranean water resources. Contrary to mineral water, spring water does not need to have any verifiable effects on health, nor does it have to contain any specific and stable amount of minerals. It also does not bear the seal of official approval.
Table water need not be of natural origin. It is an artificial mixture of tap water and other ingredients such as salt water or mineral water. Since table water is not bound to a specific spring it may be produced and bottled anywhere. It also may be sold "loosely", meaning out of dispensers and such. Contrary to mineral water, it does not require the seal of official approval.
Tap water is usually not a natural product. Unlike mineral water, it is drawn from ground and surface water. The quality of this "raw water" varies from location to location.
Contrary to mineral water, it is not of natural purity. Depending on how clean the raw water is, it is processed and purified by the waterworks. When the basic quality is not very good, it can for instance be treated with chlorine or additionally filtered through activated-charcoal.
Tap water can never be turned into mineral water. This also goes for water from so called "soda-streamers": it has the same quality and consistency as the untreated tap water and differs only in that carbonic acid has been artificially added. For people who set store by natural purity and freshness as well as healthy substances contained in "their" water, natural mineral water is the only thing suitable.