The wall of the swimming pool shall be—
(a) vertical from deck to the pool bottom;
(b) if sloped at the deep end, the upper 6 feet of the wall shall not deviate more than 1 foot horizontal in 6 feet vertical; or
(c) if a ledge is provided on vertical walls in the deep portion of the pool, it shall be fixed not less than 4 feet 6 inches below water level, and be not more than 6 inches wide with a ½ inch slope towards the pool.