A solid composition for treating cooling or heated water systems to remove scale, microorganisms and biofilm, and corrosion by-products. The composition for cooling towers and chilled water systems comprises chelating agents and an anionic surfactant. The composition for boilers and heated water systems comprises a sulfite, neutralizing amines, sodium phosphate, and, optionally, a polymethacrylate or polyacrylate polymer. A method for using such a treatment composition comprises contacting the treatment composition with substantially all parts of the water system.