Biofilms are deposits or communities of bacteria, fungi or algae that attach themselves to water-contacted surfaces and grow there. Biofilm formation is influenced by several factors: bioavailable nutrients for microorganisms, surface properties of water-contacted materials, temperature, and flow conditions. Organic substances present in the water form a covering layer on the materials, which in turn favors a settlement of microorganisms living in the water. Bacteria then produce a substance under protected conditions, which additionally protects you from external influences and brings about a growth of the biofilm and further multiplication of the bacteria. Suitable measures to prevent the formation of biofilms are water preservation or disinfection of the water and regular system cleaning.