It all depends on the last few metres
On the way from the water meter to the tap, drinking water can be contaminated by a variety of substances from the installation materials. The most notorious of these is lead. This heavy metal was used for a long time as a material for water pipes due to its excellent technical material properties. However, lead dissolves in water in concentrations which bear a risk to health and is therefore not suitable as a material for drinking water installations. It should be replaced completely as soon as possible by more appropriate materials. Since 1.12.2013 a new limit value of 10 µg/l for lead in drinking water is valid.
Materials in contact with drinking water
In the drinking water installations area, a variety of materials - such as plastics and metals for pipes, sealing materials and valves - are used which might be partially released into the water and, in doing so, would affect its quality. Organic substances in particular can also enhance the growth of bacteria and lead to the microbial contamination of drinking water.
Design and planning of drinking water installations
However, the planning, construction and operation of a drinking water installation are also critical for the quality of the water. Unnecessarily long pipes, “dead” pipe sections (dead ends), little-used pipe sections, poorly insulated pipes and insufficiently high temperatures in water heating all serve to decrease the quality of drinking water. The planning and execution of a drinking water installation have to be carried out by specialised companies.
What users can do to maintain drinking water quality
As a user you too can do a few things to maintain drinking water quality, for instance by flushing standing water (stagnant water), regularly flushing through little-used pipeline sections and alerting the operator (owner, administration) to any instances of maladministration.
Requirements on materials
With the Drinking Water Ordinance (TrinkwV) in the version amended in December 2012, the German Environment Agency was given the task of establishing the requirements on materials in contact with drinking water in the form of mandatory evaluation criteria.
Thus far, the German Environment Agency has published various guidelines in the form of recommendations for organic materials.
The four EU Member States (MS) Germany, France, the Netherlands and the United Kingdom ("4MS") have agreed on a collaboration between these 4 MS for the purpose of harmonisation of assessments of the hygienic suitability of products in contact with drinking water. The German Environment Agency is actively involved in this process.
Certification of products in contact with drinking water
The German Environment Agency does not approve products or provide certification; instead, it works out the basic and special requirements of the hygienic assessment of materials. In addition to the hygienic requirements, the components of water supply systems have to confirm certain technical requirements. Compliance with the requirements can be demonstrated through the issue of a certificate from a certifying authority accredited for the drinking water field.
When it comes to the evaluation of the contamination of drinking water with metals originating from materials, the relevant limits of the Drinking Water Ordinance must be taken into account. The German Environment Agency issued a sampling recommendation for determining the weekly average for the parameters of copper, lead and nickel set in the Drinking Water Ordinance (TrinkwV).
The following recommendation (only available in German) provides further information on the evaluation of material born contaminants in contact with drinking water.