Every CPVC fire sprinkler piping system has at least a few vertical drops with cement drips running down the pipe from the joint above. When a crack forms next to a drip, experts often claim that the failure was caused by defective installation. However, when a crack forms next to a drip, the failure mode is generally ESC caused by exposure to an incompatible chemical. Cement drips are not incompatible chemicals. So why did the crack form? The crack formed because the cement drip absorbed incompatible chemicals present in the water. We have found that the incompatible chemicals most frequently absorbed by cement drips which lead to failure are antimicrobial chemicals. Antimicrobial chemicals are often added to the water in fire sprinkler piping systems as an additive (e.g., Potter Pipe Shield) or as a lining inside steel pipe (e.g., Allied ABF pipe). Some glycerine based antifreezes also contain antimicrobial chemicals (e.g., FFS Protect OL). Cement drips in and of themselves are not a problem. However, when combined with the use of antimicrobial additives, failure can occur.