Effect of residual chlorine on copper pipes in drinking water systems

Copper pipes corrosion that transport potable water can deteriorate water quality within a distribution system, releasing high copper amounts, exceeding the maximum concentration copper for potable water standards. This study examines the influence of free chlorine on the leaching of copper in the pipes used for the distribution of drinking water. A series of tests was carried out using corrosion test coupons extractable constructed of copper material. The coupons were installed in units containing filtered water (without chlorine, 0 mg/L) and water treated with an average residual chlorine concentration of 0.85 mg/L in the water treatment plant in Azogues city, Ecuador. A corrosion test rack was also installed in a house with an average residual chlorine concentration of 0.37 mg/L. Coupons in these sites were exposed in duplicate for one, two, three and six months. The corrosion coupons were then extracted and weighed to establish the corrosion rate by gravimetric technique. Additional tests were performed in static immersion laboratory tests using drinking water with chlorine concentrations ranging from 0.25 to 5 mg/L for one month. The weight loss tests indicated that an increase in free chlorine concentration, the greater release of copper and therefore a higher corrosion rate.