Lead pipes once used routinely in municipal water distribution systems are a well-recognised source of dangerous lead contamination, but new research from Washington University in St. Louis suggests that the partial replacement of these pipes can make the problem worse.
The research shows that joining old lead pipes with new copper lines using brass fittings spurs galvanic corrosion that can dramatically increase the amount of lead released into drinking water supplies.
"Work done in our laboratory shows galvanic corrosion in joined service lines is significant and lasts for a long time," says Dan Giammar, PhD, the Harold D. Jolley Career Development Associate Professor in the Department of Energy, Environmental & Chemical Engineering at Washington University in St. Louis.
His study suggests that safety-minded, lead-pipe-removal programs at water utilities across the country actually may be increasing the risk of lead exposure for water customers.
An experiment running in his aquatic chemistry lab shows why. It features 80- to 100-year-old lead water pipes that were dug out of the ground in Washington, D.C., and shipped to his St. Louis laboratory. Some of the lead pipes have been cut and then joined with brass couplings to brand new copper pipe.
This setup mimics what happens if a utility company is replacing lead service lines and homeowners decline to have their sections of the lines replaced.
A service line runs from the main to the home. The utility owns the part from the main to the homeowner's property line and the homeowner owns the part from the property line to the house. The utility cannot replace the homeowner’s half of the line unless the homeowner gives permission and pays for replacement. In the U.S. only 10 percent of homeowners agree to the charge.
"Since you started with a whole lead pipe and you now have half a lead pipe, you might think your problem would be half of what it was or — maybe — completely unchanged," Giammar says.
His experiment reveals that instead, it could be far worse. The joined lead-copper pipe in his lab releases five times more lead than did the original lead pipe.
The lead is released by galvanic corrosion, a process set up whenever two dissimilar metals are immersed in a conducting liquid.
The same thing happens if lasagna or another acidic dish is made in a stainless steel pan, covered with aluminum foil, and placed in a refrigerator. The two metals and the lasagna act as a galvanic cell, and some of the aluminum may migrate out of the foil and plate out on the surface of the lasagna.
Washington University in St. Louis
