Impact of Water Heaters on the Formation of Disinfection By‐products

This study examined the effect of water heaters and home‐heating scenarios on the formation and decomposition of disinfection by‐products (DBPs). Residential concentrations of DBPs were investigated in cold and hot tap water samples from 18 houses equipped with conventional water heaters or on‐demand, tankless heaters. The houses were served by a western Massachusetts water system. On‐demand heating without long‐term storage of hot water resulted in little or no change in DBP formation. In contrast, the research indicated that long‐term storage could lead to an increase in trihalomethanes, haloacetic acid, and chloropicrin, whereas the concentrations of dichloroacetonitrile and trichloropropane resulted from competition and decomposition. In the bench‐scale study for this article, laboratory incubation and different heating scenarios (short‐term and long‐term) were tested to confirm the effect of stagnation and high temperature on DBP concentrations in different types of heaters.