Chill water, also called chilled water systems, are fundamental to virtually all larger building properties.  Unlike condenser water service, they benefit from far lower internal corrosion activity but then have a potential secondary corrosion front occurring to the outside.  The smaller lines to any chill water system are the most vulnerable due to lesser wall thickness, threaded construction, thinner insulation, and their placement often in areas of higher humidity – such as within fresh air plenums and at perimeter building columns.

A common issue called CUI, for corrosion under insulation, applies to the failure of the insulation to protect the pipe exterior.  This is less a failure of the insulation itself and more of a design, installation, and maintenance issue.  Nevertheless, CUI can easily destroy a chill or cold water piping system.  It is a significant problem for both 2 pipe and 4 pipe HVAC systems.

While internal corrosion activity is generally uniform throughout the system and controllable through chemical treatment, external corrosion varies wildly, and cannot be predicted.  Critical side stream water filtration is almost never installed in its design phase, and only considered once a problem becomes too significant to ignore.  For most heavily damaged piping systems, their early retirement has been due to the combination of inadequate internal corrosion control compounded by insufficient insulation which has been inadequately installed.

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