Lead and Copper Rule

Corrosion immersion testing - Chloramine conversion project set-up

In early 2020, the City of Craig’s drinking water treatment plant will switch disinfection treatment from standard chlorination to using chloramines, and to the disinfectant  residual will change from free chlorine to chloramines. This change is being made to address frequently low free chlorine residuals in their distribution system. This change may impact distribution system corrosion as well as lead and copper levels at customer’s taps. Instead of waiting to see if any negative corrosion impacts arise, Craig and the department have teamed up for an experiment to test the potential corrosion impacts of the chloramine treatment change. 

The experimental testing approach is an immersion study—also known as a coupon study—which involves putting small metal samples (or coupons) in test waters to see if the lead and copper concentrations are different. For Craig, the test waters are the current free chlorine potable water (control scenario) and future chloramine water (chloramine test scenario). Since materials vary in the distribution system, three materials are being tested: lead, copper with lead solder, and brass. Each material will be tested under current and future water conditions, with the water in the jars being changed out three times per week (see the experimental set up in the photo above). 

For the first half of the 12-week experiment, all of the sample jars are filled with the current free chlorine water. This stabilizes the metal samples and models the current conditions of the distribution system pipes. For the rest of the experiment, half of the jars are filled with the current free chlorine water (control scenario) and half the jars are filled with the future chloramine water (chloramine test scenario). The city’s water treatment staff create the formulated chloramines water and sampling water and refresh the jars three times per week. They then combine the three samples into a single sample per week, which is called taking a weekly composite sample. Each week during the testing period, the Craig staff sends the lead and/or copper composite samples to the state lab for testing. The testing began in early October 2019, and we expect results in early 2020. 

Please note that the experiment will not model the lead and copper concentrations at customer’s taps. Instead, the immersion study will give relative results. In other words, the study as designed will identify if the switch from free chlorine to chloramines will potentially increase the lead and copper from different pipe materials once chloramines are in full-scale use. 

For more information on immersion testing please see the department’s Lead and Copper Corrosion Bench-Scale Testing Guidance Manual.

➽ Tyson Ingels and Melanie Criswell, drinking water engineers