Five case histories are described where standard Types 304 or 316 stainless failed prematurely by localized corrosion in fresh waters that nominally would be considered to be non-aggressive. These waters were, however, very aggressive because of the effects of microbes, manganese or chlorination, depending on the particular case. In each of these cases the standard stainless steel was replaced with one of the high performance stainless steels with good results.