As you already 清理干净了管子入口处, the problem is not 排水管里面堵死了. Another problem migh have caused your problem. If your existing shingles at the roof edge is not long enough (because of the roof age), water can splash onto the roof edge and the fascia below, eventually 水从房檐直接滴下来 and causing rot at the foundation. It is better to fix it as soon as possible.