During a year‐long study, weekly samplings and analyses were conducted at five US water treatment facilities—two coagulation–filtration plants, two iron‐removal plants, and one lime‐softening plant. These municipal treatment facilities had a treatment capacity of 1.4–600 mgd (5.2–2,271 ML/d). The study was conducted to evaluate the performance of these full‐scale plants for consistently removing arsenic (As) from raw water containing 2.6–97.9 μg/L of total As. The two coagulation–filtration plants and one iron‐removal plant consistently removed As to < 10 μg/L; however, the other iron‐removal plant and the lime‐softening plant did not.