Corrosion is a common event occurring to almost all piping systems, although its impact, financial loss, and potential threat varies greatly.  The failure at a vent stack line behind a bathroom wall may not be noticed for years, whereas the total thread separation failure of the galvanized steel domestic water riser next to it will be felt by many tenants within a matter of minutes.  A pinhole leak at a roof condenser water main presents significantly less threat of damage than the same size leak within a critical data center  server room.  The deposits produced by a 5 MPY corrosion rate at a 24 in. condenser water main will not alter its flow rate, but at a dry fire sprinkler system, can easily stop all water flow to the sprinkler heads  during a fire emergency.

Most piping systems are susceptible to multiple forms of corrosion occurring either independently or in combination.  Copper domestic water lines are vulnerable to pitting and galvanic attack as well as erosion, cavitation, and unfavorable water quality.  Internal and external corrosion at chill water and dual temperature systems double the level of threat, whereas internal corrosion is generally the only concern for most other systems.  Even within  individual piping systems, varying corrosion conditions can be identified throughout its different pipe sizes, between its supply and return lines, from its top to lowest floors, and between vertical or horizontal runs.

This series of Photo Galleries illustrates the various corrosion problems and failure types associated with the piping systems common to most building properties.