Originally Posted by cyccommute

I said “micro-organisms”. Water is tested at the treatment plant for micro-organisms and reporting requirements are set by Federal law. Lead in water is not likely to come from the treatment plant nor the water source. Lead pipes were used to provide houses with water from the mains. The lead will oxidize and form a layer of insoluble lead oxide or lead carbonate inside the pipe. Phosphate buffer is added to the water at the treatment plant to maintain the protective layer. If the water source has too much chloride in the water, this can cause the protective layer to fail and the lead pipe to start leaching lead into the water.

The problem, however, is that the lead isn’t at the treatment plant. Discovering lead in the tap water of your house depends on testing the water in your house. The measurement of micro-organisms and dissolved metals in the source water is quick and is done often. The measurement of metals at the end of the pipe…i.e. your faucet…isn’t done regularly (or at all) so it takes a while to find problems. Flint, MI was a wake up call and most municipalities are currently putting programs in place to remove lead pipes but there are so many of them, it is going to take a while.

If you want to get deep into the weeds, here’s an article on Flint from the American Chemical Society. It’s very readable and applies to all lead pipes.