In the morning the first coffee is to be made. No water has been drawn from the kitchen tap since the previous evening. At the same time you know little about the house’s pipework. Two questions should be kept separate: the general handling of stagnation water and the technical clarification of a possibly problematic installation.
Understand the general advisory narrowly
The Umweltbundesamt recommends in its consumer information that drinking water which has stood in the installation for longer than four hours should not be used for the preparation of food and drink. It should be run off; fresh water is perceived as noticeably cooler after the described temperature comparison. [WASSER]
This everyday recommendation is not a laboratory test and not an approval of unknown pipes. A cooler perception does not answer which materials have been installed in the building or whether a specific contamination is present. In the event of an official restriction or a known anomaly, that special instruction must be observed; this article does not replace it.
Clarify what is known about the house separately
Ask the owner or management for any information available about the drinking water installation and for known particularities. The statement about the good quality of the supply water does not automatically answer the question about the condition within the building. The UBA explicitly distinguishes the supply from the last metres of the installation inside the building. [WASSER]
In the fictional example a new resident receives the general analysis from her water supplier. That does not clarify anything about old pipes in the building. She keeps the analysis as information about the supply and requests the missing building information separately. She does not try to decide the question of materials herself by taste or a photo of a single fitting.
Do not turn an everyday tip into a renovation method
If the installation has not been used for a long time, has been altered, or a specific problem is known, a suitable technical opinion is required. The brief advice for stagnant water is not extended here into the procedure for recommissioning a plant that has been out of service for a long time. The article also does not prescribe thermal treatment or self-sampling.
Work on the drinking water installation should, according to the UBA recommendation, be carried out by specialist firms. [WASSER] Please, when requesting an investigation or measure, ask that the task and the result be related comprehensibly to the affected installation. A general statement about a filter or a fitting alone would be too imprecise for that purpose.
Keep everyday guidance and outstanding technical questions side by side
Your documentation can be brief: general usage recommendation, known information about the building and a clearly designated question that is still open. If a concrete suspicion is not clarified, routine should not appear as evidence of its having been dealt with.
The information applies to Germany and concerns the described normal household advisory. It is not an individual health assessment and not a technical approval. In the case of differing requirements or anomalies, the competent specialist bodies must be involved.