"This research program was initiated to determine whether adding zinc orthophosphate to potable water would sufficiently coat an asbestos-cement pipe with zinc to prevent asbestos fibers from entering the water. Storage tanks and chemical and feed pumps were set up at each of the Greenwood, SC, water treatment plants, and zinc orthophosphate was fed into the system at an average rate of 0.3 mg/L. Two sections of new asbestos-cement pipe were installed to represent a low-flow and a high-flow water condition; they were removable for testing. Samples were periodically tested to determine the number of asbestos fibers in the water. The two pipe sections were removed and examined for the amount of zinc deposited on the surface. Although routine tests, such as pH and alkalinity, showed no significant changes during the study period, asbestos fibers in the water decreased substantially. Electron microscope photographs and energy dispersive X- ray spectra analyses showed coatings of zinc products on the two pipe samples. Thus, adding zinc orthophosphate under the existing water quality conditions reduced or prevented corrosion of asbestos-cement pipe."