Conn. Gen. Stat. § 29-265b
Rain sensor devices for automatic lawn sprinkler systems.
(b) A municipality may, by ordinance adopted by its legislative body, require that any automatic lawn sprinkler system, the installation of which begins on or after October 1, 2003, shall be equipped with a rain sensor device or switch that will automatically override the irrigation cycle of such sprinkler system when adequate rainfall has occurred.
(c) Any automatic lawn sprinkler system installed on residential property on or after July 1, 2010, shall be equipped with a rain sensor device or switch that will automatically override the irrigation cycle of such sprinkler system when adequate rainfall has occurred.