This invention provides a method of controlling microbes in a drinking line system when poultry and/or swine are absent from the area where the drinking line system is located. The method comprises I) contacting the drinking line system and an aqueous microbiocidal solution； and II) flushing said drinking line system with water and/or an aqueous solution comprising one or more scale removers at least once after said contacting with said aqueous microbiocidal solution, wherein said aqueous microbiocidal solution is formed from components comprising water and a concentrated aqueous biocidal solution selected from A) an aqueous biocide solution having an active bromine content of about 50,000 ppm or more, which solution is formed from components comprising water and (i) bromine chloride or bromine chloride and bromine, with or without conjoint use of chlorine, and (ii) overbased alkali metal salt of sulfamic acid and/or sulfamic acid, alkali metal base, and water, wherein the relative proportions of (i) and (ii) are such that the atom ratio of nitrogen to active bromine is greater than 0.93, and wherein the pH of the composition is greater than 7, or B) an aqueous biocide solution formed from components comprising water and (i) at least one bromide source selected from ammonium bromide, hydrogen bromide, at least one alkali metal bromide, at least one alkaline earth metal bromide, and mixtures of any two or more of the foregoing, (ii) a chlorine source, optionally (iii) at least one inorganic base, and optionally (iv) sulfamic acid and/or a metal salt of sulfamic acid, or C) a combination of A) and B). Any degradation of the materials of the drinking line system from contact with said aqueous microbiocidal solution is minimal.
