Hi,
I'd plan the developpment either one way or another:
arduino -> sensors way: simulate the sensors input in a short routine of your software. Do ignore the rest of the -software- project and isolate the program portion that warns if the flooding sensors are sending 1,1,1, ... . Ignore the transmission hardware too (by the moment).
sensors -> arduino way: Make sure that the sensors do give "1" when they should. Mount them close to your lab and actuate them by hand in the first steps. Do check the "1" and "0" on the transmission input screws equipment.
Once you have solved those steps, you can check the transmission (once again do isolate the software and simulate everithing else) software/hardware.
And, then, connect everything and cross your fingers ...
Good luck
Regards