Wilkerson Drain Manual Drain, B18,B28,CB6,F16,F18 F26,F28,F30,F35,M16,M26,M30,M35. Wilkerson Drain. Manual override drain. Used on F16, F18, F26, F28, F30, F35, M16, M26, M30, M35, CB6, B18, B28.