Waste outlets serving showers shall be at least 2 inches (50 mm) in diameter and, for other than waste outlets in bathtubs, shall have removable strainers not less than 3 inches (75 mm) in diameter with strainer openings not less than 1/4 inch (6 mm) in minimum dimension. Where each shower space is not provided with an individual waste outlet, the waste outlet shall be located and the floor pitched so that waste from one shower does not flow over the floor area serving another shower. Waste outlets shall be fastened to the waste pipe in an approved manner.