Yes, I know what a sanctuary city is, but I didn't understand the connection to such a sign. It's actually in Philadelphia, but it is literally the only location I have ever seen such a sign in the entire city, which baffles me. It is clearly not a city ordinance to have them. The best I can come up with is that under normal circumstances, toilets are connected to regular tap water; the same source as the sinks. So these toilets must be connected to a non potable source, therefore they have to be labeled. I guess this is in case someone actually was tempted to dunk their water bottle into the bowl! Or, maybe more if there was some sort of emergency, and people were actually holed up in the school and surviving on limited access to food and water. I still have no idea what connection this would have to a sanctuary city, or to a high population of immigrants (two very different topics, since the large majority of immigrants are in the US legally). I have done a lot of travel and my sense is that no one drinks from toilets, no matter what country they are from!