Drinking water is not a chemically passive substance. As soon as it flows through or stands in household installations, it interacts with the materials used. Plastics, elastomers, seals, and flexible hoses can release traces of additives, monomers, or degradation products into the water. This process is called material migration and is a central, often underestimated factor for water quality in the home.
Material migration is not an isolated case but a well-known phenomenon in material science. In addition to the base material itself, polymers contain functional additives such as plasticizers, stabilizers, or cross-linking agents. Under the influence of time, temperature, and contact surface, these substances can migrate from the material into the surrounding water. Studies show that elevated concentrations are measurable, especially in new installations or after longer stagnation periods [German Environment Agency, Assessment of materials in contact with drinking water, https://www.umweltbundesamt.de/publikationen/bewertung-von-materialien-im-trinkwasserkontakt].
The extent of migration strongly depends on operating conditions. Longer residence times increase substance transfer, as do elevated temperatures. Hot water pipes, mixing taps, and flexible connection hoses therefore often show higher migration rates in studies than rigid cold water pipes. Surface properties also play a role: soft elastomers offer larger effective contact surfaces than smooth metallic materials [World Health Organization, Guidelines for drinking-water quality – materials, https://www.who.int/publications/i/item/WHO-FWC-WSH-17.05].
Material migration is considered by regulations, but with clear limits. Testing procedures evaluate materials under standardized conditions and set permissible release quantities. However, these tests represent average scenarios. Real households differ significantly in terms of usage profiles, temperature curves, and stagnation times. Accordingly, individual exposures can be higher without exceeding formal limit values [European Commission, Drinking Water Directive (EU) 2020/2184, https://eur-lex.europa.eu/eli/dir/2020/2184/oj].
Material migration is particularly relevant in the context of chronic low-dose exposure. The quantities of substances released are usually small but act continuously over long periods. Studies on overall exposure show that drinking water can make a measurable contribution to the intake of certain plastic additives, especially when multiple sources combine [European Food Safety Authority, Assessment of plastic additives, https://www.efsa.europa.eu/en/topics/topic/plastics].
For everyday life, this does not mean that tap water is unsafe. However, it illustrates that water quality does not solely depend on the supplier. Materials, usage behavior, and residence times determine what actually ends up in the glass. Particularly after longer periods of disuse or with warm water, material migration can become more significant.
Drinking water is not only created at the waterworks.
It is further shaped in the home.
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