The Ontario Building Code | Traps for Storm Drainage Systems
22.214.171.124. Traps for Storm drainage Systems
(1) Where a storm drainage system is connected to a public combined sewer, a trap shall be installed between any opening in the system and the drain or sewer, except that no trap is required if the opening is the upper end of a leader that terminates,
(a) at a roof that is used only for weather protection,
(c) not less than 1 800 mm from a property line.