Wet, discolored, or damp insulation is the first sign of insulation failure and potentially an external pipe corrosion condition.  This is caused by inadequate, improperly installed, poorly maintained, or inappropriate insulation having allowed moisture to penetrate to the cold pipe surface.  Once moisture reaches the pipe it condenses into water and then travels its most favored path to impact a much larger volume of pipe.  Various factors influence this condition – the most significant being insulation thickness, pipe temperature, and area moisture content.

Similar to weathering at an outdoor steel condenser water system, the problem is almost always immediately apparent.  One exception to this rule is for soft rubber or foam insulation which not only traps condensed water inside, but also rarely shows any discolorizaton to its black surface.  Water droplets on the floor unquestionably define that the insulation has failed, is saturated, and that it can hold no more water.  Brown spots, water marks, discolorization, and crystalization deposits are another clear indication.  With paper and fiberglass offering excellent growth substrates, mold adds a further threat to all building occupants.

In short, if everyone runs for buckets when the insulation is cut open, thinking they may have cut through the steel pipe, the insulation failed long ago!

Once wet insulation is identified, further investigation should be conducted in order to identify the cause and impact to the pipe followed by replacement with the correct insulation.  If moderate to heavy external pipe damage has occurred, further action will be required depending on its severity.