Photo Gallery B7:  Erosion Corrosion

Water flow induced erosion is primarily a mechanical force based deterioration although chemistry usually plays some role.  It is heavily dependent upon water velocity and the “softness” of the piping material, with secondary factors such as water chemistry, piping layout, and particulate content also involved.  While a potential threat to most HVAC and plumbing piping systems, it is far more common for copper pipe providing domestic water service.

While multiple causes exist, copper pipe erosion is primarily related to higher than normal water velocity which then produces cavitation immediately downstream of elbows, tees,valves, and other fixtures.  Even the smallest interruption to laminar flow, such as the failure to bevel or camfer the pipe ID can lead to cavitation – an issue we have been raising for various forms of pressed copper pipe assembly alternatives to soldering.

Its impact is amplified by heat, which is why a higher level of deterioration is commonly found at the hot water lines, and those closest to the boiler.  Softened water, and especially RO water, also play a significant role since they remove key chemical elements which actually protect the copper.  The demand for more control over water flow, and the introduction of higher pressures and flow control devices, has also increased the incidence of erosion problems.  When combined, failures can occur in under 5 years, and resemble a mechanical etching or machining away of the pipe wall.

Brass is also susceptible to erosion under certain conditions, but far less of a concern for any form of steel, cast iron, or ductile iron pipe.