TC reported Fire external alarm at FDT car. Staff (BGB) checked and feedback no sign of heat or smok e. Rear T415 did a line clear and confirmed no abnormalities . ~~~~~ TC reported Fire external alarm at FDT c     #3621 Fault code 721,#2621 fault code 721.Further check found both smoke detector water ingress.Replace smoke detector and function test ok. #3621 smoke detector- Not: 2466430 #2621 smoke detector- Not: 2466429 Done by Saini/Zulq.  01/03/23