The objective of this study was to determine if potable water containing aluminum, high chlorine residual and relatively high pH can cause pinholes in copper tube. To our knowledge this is the first time the phenomenon of pinhole leaks have been reproduced in the laboratory as it occurs in the field. It therefore proves that "aggressive water" alone can cause the problem of pitting. The role of flow, pipe orientation and hypothesized surface defects were directly examined as part of this evaluation. Pitting increased for pipe sections with high flow and for sections of straight pipe exposed to hydraulic conditions near bends. Copper pipe sections polished to a mirror like finish to remove surface defects were also severely attacked. Includes 18 references, tables, figures.