Rare corrosion failures of stainless steel are reviewed in the paper. The cases originate from low chloride waters like potable water or fresh water in the temperature range of 15-25°C. Under such conditions full resistance of austenitic stainless steel like AISI 316 is usually expected. In all cases corrosion was associated with the build-up of dense corrosion products (tubercles), which suggests microbial influence on corrosion. This is further supported by ennobled potentials in most cases. Based on the observations collected through failure investigations, possible theories for the cause of corrosion are discussed. Precautions to avoid corrosion e.g. when doing hydrostatic testing are also discussed.