Many brass fittings and mechanical devices (brass = copper-zinc alloys) are widely used in potable water systems and are often used alongside copper or plastic (i.e. cross-linked polyethylene or PEX) piping. Brass failures in premise plumbing are relatively rare but do occur because of a variety of non-uniform corrosion phenomena including dezincification pitting lead leaching and erosion corrosion (Sarver 2010). While there is extensive literature on dezincification erosion corrosion of brass has not been carefully examined in potable water systems to the best of our knowledge.Erosion corrosion has been a widely recognized failure phenomena in potable water systems for at least 7 decades but is still poorly understood. Experimental studies on copper piping systems have shown that erosion corrosion worsens at increased temperatures and high flow rates (Knutsson et al. 1972). While brass alloys are often described as more resilient than copper similar trends can be expected for the former to fail. The rapid adoption of hot water recirculation systems is further increasing the likelihood of damage owing to continuous exposure of the fittings and devices to flowing hot water. A whole host of “lead-free” brass products have flooded the market after the passage of the 2011 Federal Reduction of Lead in Drinking Water Act (SDWA 2011) in the U.S. last year; whether these have been adequately tested towards their propensity to fail because of erosion corrosion is doubtful.Recent investigations of erosion corrosion in copper plumbing have hinted at precipitation of water hardness (i.e. Calcium Carbonate CaCO3) as a likely culprit (Roy and Edwards 2014). High temperature/pressure conditions achieved during water heating can precipitate hardness as aragonite or calcite particulates some of which are harder (material-wise) than the brass plumbing components. We hypothesized that repeated impingement of aragonite particles suspended in water can significantly accelerate brass failures. Recirculating 5ft x 4ft PEX pipe rigs (i.e. four PEX pipes in a rectangular loop; two 5ft pipes are horizontal while the 4ft ones are vertical) with ½” brass elbow fittings from a commercial vendor were constructed to study the role of suspended aragonite particulates. Fully penetrating leaks occurred in brass devices occurred in 13.5 days at 10 ft/s 50-55°C and pH 7.5. A second recirculating rig at pH 10 failed 9-10 days later. The control condition without particulates was undamaged. These results indicate that a synergistic mechanism of erosion and corrosion are at play contributing significantly to rapid failures. Subsequent experiments will examine the role of velocity particulate size temperature and disinfectants in brass fittings which are expected to be completed by January 2016.References:

1. Knutsson L. Mattsson E. and Ramberg B.E. (1972). “Erosion Corrosion in Copper Water Tubing.” British Corrosion Journal. 7 208-211
2. Roy S. and Edwards M.A. (2014). “Erosion Corrosion of Copper as a function of velocity temperature and water hardness”. AWWA Annual Conference and Exposition Boston MA June 10-14 2014
3. Sarver E. A. (2010) “Insights into non-uniform copper and brass corrosion in potable water systems” (Doctoral Dissertation) Retrieved from Digital Library Archives here: http://scholar.lib.vt.edu/theses/available/etd-11052010-155843/ (ETD-11052010-155843)
4. Sarver E. and Edwards M. A. (2011) “Effects of Flow Brass Location Tube Materials and Temperature on Corrosion of Brass Plumbing Devices Corrosion Science 53 (3) pp 1813-1824
5. Safe Drinking Water Act (SDWA 2011). “Reduction of Lead in Drinking Water Act” Jan 4 2011 [S. 3874] Available here: http://www.gpo.gov/fdsys/pkg/BILLS-111s3874enr/pdf/BILLS-111s3874enr.pdf