My city facilitated that a decade or two ago by building new indoor reservoirs specifically for water treatment. Now we have a small handful of facilities set upon for massive chemical insertion and holding about half a day’s worth.

That being said, you’d still need the cooperation of people at each site, security at each site, truckers and suppliers. But that’s only one city: multiply that by the thousands of cities plus now you’d need huge amounts of chemicals that someone would surely question. That’s a lot of moving parts.