The polymer must be used at levels not to exceed 20 ppm in the feed water. The polymer must not be used at pressures above 1,000 pounds per square inch gauge (psig). The polymer has a molecular weight range of 7,500 to 15, 000. The polymer comprises at least 99 mole percent acrylic acid and 1 mole percent sodium styrene sulfonate. Specific substances permitted for use as boiler water additives complying with 21 CFR 173.310 may be used in the subject boiler water additives subject to any limitations in the authorizing regulation or notification. The finished boiler water additive must meet any applicable specifications prescribed in 21 CFR 173.310.