Photo Gallery A7:  Pressed Copper Failures

Copper pipe generally provides trouble free service.  Although not immune to corrosion and actually more vulnerable to specific issues such as velocity induced erosion, copper pipe is being turned to more and more as evidence of lower service life for steel pipe increases.  In cases where wall thickness has been high yet failures have occurred at elbows, metallurgical testing has commonly identified erosion caused by the almost insignificant failure to camfer or bevel the inside diameter of each connection.  As a result of this very minor installation defect not well recognized, turbulence and cavitation at the downstream side of the connection can produce severe pitting resulting in its failure.

For pressed copper pipe assembly systems, in which each fitting is swaged or squeezed onto the copper pipe with an internal O-ring providing the water retaining seal, a very similar if not more significant amount of turbulence is created.  This is especially true where the previously round shape of the pipe is swaged into a hex shape at different locations along its path; the water then experiencing a higher level of turbulence.

Of course, many other factors lead to advanced copper pipe failure, such as high water velocity, heavily softened water, RO or DI water, elevated temperatures, and deposited rust, etc., often in some combination.  Greater vulnerability of the fittings themselves are also evident – as we show here at many valve bodies.

Erosion / cavitation related copper pipe failures at sweated pipe can take decades to reveal themselves dependent upon many contributing factors.  Our recent findings of advanced failures at newer pressed copper connections suggests that a similar but potentially even more aggressive failure mechanism has yet to be fully realized.