Water treatment bypass loops combining ozone and chlorine injection, and an adaptable clamp apparatus to support efficient retrofit installation of forward bypass loops (around filters) or reverse bypass loops (around pumps) and associated equipment are disclosed. Combined injection of ozone and chlorine exploits high oxidation potential of ozone to enhance oxidation effectiveness of chlorine while still retaining longer lived residual effectiveness of chlorine, particularly against biological and organic contaminants. A method for reducing costs of salt chlorine generation electrolysis cells and power supplies by using ozone to reduce deposit buildup on electrode plates is also disclosed, as is an apparatus for generating chlorine for use in water treatment in bathing facilities without requiring addition of sodium chloride or other halogen salts to water in a swimming pool or spa.