Metals in drinking water are often associated with source water or treatment plants. In reality, elevated metal concentrations usually develop within household plumbing systems. Pipes, fittings, and faucets play a decisive role in shaping what reaches the tap.
Copper is a common example. Widely used in plumbing, copper is generally approved for drinking water installations. However, studies show that copper concentrations can increase significantly after periods of stagnation. Corrosion processes at pipe surfaces are influenced by pH, temperature, and contact time. The German Environment Agency emphasizes that elevated copper levels are typically detected at the tap rather than in the distribution network [UBA, Copper in drinking water, https://www.umweltbundesamt.de/themen/wasser/trinkwasser/trinkwasseraufbereitung/kupfer-im-trinkwasser].
Nickel release is commonly linked to chrome-plated fixtures and stainless steel alloys. Newly installed components can release measurable amounts, particularly during the first months of use. Research shows that nickel levels are highly dependent on stagnation time and temperature and can be significantly reduced by flushing before use. Regulatory guidance therefore treats nickel primarily as a plumbing-related parameter [World Health Organization, Guidelines for Drinking-water Quality, https://www.who.int/publications/i/item/9789241549950].
Lead represents the most critical case. Although lead pipes have been banned in many countries, they remain present in older buildings. Additionally, lead-containing brass alloys can contribute to release. Scientific evidence indicates that even very low lead concentrations can have long-term health effects, particularly in children, and no safe exposure threshold has been identified [European Food Safety Authority, Lead exposure assessment, https://www.efsa.europa.eu/en/topics/topic/lead].
Regulations reflect this reality by applying metal limits at the point of use. The European Drinking Water Directive explicitly recognizes household installations as a key source and requires materials and systems that minimize metal release [European Commission, Drinking Water Directive (EU) 2020/2184, https://eur-lex.europa.eu/eli/dir/2020/2184/oj].
For everyday use, this means metal exposure is strongly influenced by how water is used and how installations are designed. Stagnation, warm water, and new components increase the likelihood of elevated levels. Flushing can reduce short-term exposure but does not replace appropriate material selection and installation design.
Metals rarely come from the treatment plant.
They are introduced in the final meters.
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