Drinking water

Drinking water is water that is of sufficiently high quality so that it can be consumed or utilized without risk of immediate or long term harm.

Furthermore technical requirements are to be ensured, such as no corrosiveness against pipes and prevention of sedimentation.

Drinking water must not contain pathogenic microorganisms (pathogens), likewise a minimum concentration of mineral nutrients should be contained. The most common mineral nutrients are calcium-, magnesium-, carbonate-, hydrogen carbonate-, and sulfate-ions.

The sum of their concentration is monitored as hardness grade of water. In Germany the DIN 2000 and the drinking water ordinance sets the standard for the drinking water quality.


Water must flow !

  • a complex pipe network with "dead strings" and little used pipe ends
  • long time of stagnation
  • fire extinguishing device (wet pipes)
form an ideal basis for contamination in the pipe system. Over time a biofilm is build in the warm- and cold water sytem.


A biofilm is a structured community of microorganisms encapsulated within a self-developed polymeric matrix and adherent to a living or inert surface. Biofilms are also often characterized by surface attachment, structural heterogeneity, genetic diversity, complex community interactions, and an extracellular matrix of polymeric substances.

Biofilms are usually found on solid substrates submerged in or exposed to some aqueous solution. Stagnant water supports the biofilm effect and forms the optimum nutrient medium for germs.

Sediments due to calcareous water as well as corrosion in pipes and water tanks support this film formation. Germs can multiply in biofilms and jeopardize the drinking water system.

Therefore drinking water pipes are especially exposed to biofilm formation, as bacteria can grow heavily there.


Germs are microscopical small organism. There are more than 6000 species, living everywhere in the air, in the water and in the ground, as well as in plants, animals and humans.
From a human point of view there are:

  • useful bacteria, mainly living in the ground and in the water
  • harmful bacteria, pathogen of infectious diseases (legionella)