If a tower has not been used, is in a stagnant state or is highly fouled and needs cleaning, a bacteria test must be performed first to determine bacteria levels. If bacteria levels exceed the Center of Disease Control’s regulation of ten to the fifth levels, the tower must be disinfected. High levels of chlorine and sodium bromide are to used along with a biocide, either gluteraldehyde or isothiazalin, and a biodispersant to insure that all traces of biological growth are killed. These chemicals must be recirculated for 2-6 hrs. before the actual mechanical cleaning process begins. Tower must be retested for bacteria conditions prior to discharge of chemicals and the mechanical process can begin.