|Not likely to make you feel confident.|
So I stopped to use the Ladies' in Grand Central Station, and when I went to wash my hands, found the sign above posted over every faucet.
Not sure what rattled me more: the assertion that the water is "most likely" safe (which I read to mean, "You won't die if you wash your hands in it. At least not immediately."), or the counsel to try lighting it and see if it burns.