Lye is actually a very common household chemical. It's used in cooking and even grooming products--quality shaving creams have sodium hydroxide or potassium hyd

Lye is actually a very common household chemical. It's used in cooking and even grooming products--quality shaving creams have sodium hydroxide or potassium hydroxide. You can easily buy large containers of the stuff everywhere, including your local hardware store and, traditionally, grocery store. (These days you may need to go to a speciality grocer to find food-grade lye in bulk.) The nice thing about lye is that it's typically sold in solid form, excepting in one of the most common household products, drain cleaner. Drano is sodium hydroxide in solution with aluminum, with which reacts in the presence of water, presumably to help mechanically break up clogs. Solid lye tends to be safer as there's less chance of ingestion, and less chance of it lingering on your skin--it turns your skin to soap. Much more dangerous is stuff like sulphuric acid, which you can buy (at least in California) in concentrations of over 95% at the hardware store as Rooto and similar drain cleaners. That stuff is nasty as its in liquid form, easy to spill and even inhale as an aerosol. Also not a good idea for pipes despite how they're sold because such acids are hell on cast iron--i.e. what main sewage drains are made out of in older buildings and in jurisdictions that aren't favorable to PVC. There are so many ways for evil people to do evil things it's amazing (and, frankly, fascinating and even instructive) that it doesn't happen more often. I'm curious to see how the situation will change as it becomes easier to be evil while remaining anonymous and remote. Still, I imagine it would be extremely difficult if not impossible to actually cause significant harm by changing the concentration of lye in the water suppler. For example, I'm skeptical that there would be enough lye in the dispenser at the treatment facility to cause serious harm. The worst effect would probably be disrupting the pH of the water system and possibly causing other ill effects, such as by leeching lead or rendering antimicrobials less effective.