Drinking Water quality on customer’s tap – correlation with materials used in domestic distribution systems and recommendations for quality improvement

Drinking water produced in water plants almost invariably fulfils the water quality requirements set in European Union Drinking Water Directive (Council Directive 98/83/EC, 1998). However, the DWD requires that water quality should also meet the requirements at the consumer’s tap. When drinking water is distributed through pipelines, biofilms will grow on the inner surface of the pipes and soft deposits (organic and inorganic matter) and several metals will accumulate to the pipelines. Corrosion of household plumbing systems is an important source of trace metals found in tap waters. Significant levels of trace metals could be detected after stagnation of the water in distribution system, especially during night – time. In order to get an overview of the overall current contamination levels of drinking water at the point of consumption were collected and analysed more than 600 samples from cold line-pipe with three different sampling procedures (first draw, fully flushed and randome daytime). A monitoring plan was developed and the content of metals was analyzed from drinking water samples collected directly from consumers and from the municipal distribution network. In the study were correlated data regarding metals concentration in customer’s tap water and materials used in domestic distribution systems in order to investigate influence of materials to the tap water quality.