I just recon its just pretty broad signage. If the water is that bad in the Natti dunnies, why bother washing your hands in the public toilet anyway? You've got shit on your hands either whether you do or not.
Probably would have made a difference if they said irrigation water on the toilets sign.
I had been told that Natti was having water trucked in from elsewhere. i figured this was being pumped into some sort of ' town water suply' but guess it must be a neverfail truck or whatever.