As a matter of principle and pursuant to Article § 823 of the (German) Civil Code (BGB), property owners are responsible for ensuring that their property cannot pose a danger to its residents and the visitors (duty to maintain safety). If they fail to keep their premises safe they are liable for damages.
The dispensation of justice makes it absolutely clear: The property owner will only have performed his duty to maintain safety, if he regularly checks the operational reliability of the technical facilities installed. This shall be done on the basis of the generally recognized rules of sound engineering practice. If the property owner does not have the necessary expert knowledge, he must commission a specialist firm with the job. If he fails to observe the deadline of an inspection period as specified in the technical rules, he shall be liable for damages (see Higher Regional Court of Saarbrücken, NJW 1993, 3077).
Gas pipes need to be checked for leakages, drinking water has to be clean and free of potentially pathogenic bacteria, electrical lines must be tested, etc.
If you utilize complex technology to operate your building you need a heightened awareness for liability issues due to a considerably higher risk for injuries and damages if the technology applied fails to work properly.
The law demands water tests every year if the site is of public use. Residential building where the water is provided for merely commercial purposes must be tested in 3-year-intervals. If the property owner or the plant operator fails to carry out the checks within the deadlines set and a residents acquires a pneumonia his negligence (to perform the test in time) constitutes a prima facies evidence that if the test had been performed according to the legal requirement the damage would not have occurred.