Upon arrival at Cavite, Philippine Islands, "Rainbow" became the flagship of Submarine Flotilla 3 (later designated Submarine Division), Asiatic Fleet. She also served as tender to Submarine Division 12 and sometimes assisted in tending the "boats" of Submarine Division 18. Except for a visit to Hong Kong (11-31 October 1921), she remained in the Philippines until 23 April 1923. She then sailed with the Submarine Divisions of the Asiatic Fleet and tender "Finch" to serve along the China Coast at Shanghai, Chefoo, Chinwangtao, Woosung, and Amoy.