Boiled water is sterile. And if you chill it immediately after boiling, and pin what you recon within a couple days it's a safe bet nothing bad will have had time to grow. Think what you will, I have personally done it many times as sterile water and BAC water is not available for me locally. I can get it online sure, and normally I do. Shit happens. I've had to part ways with vials of BAC to help people out and found myself In need and rather than break my protocol and wait on the mail I've used distilled water and never had not one issue with it. Subq shots are not the same as IV your immune system will still protect you. And fwiw, junkies slam dope with whatever liquid they can find, tap water toilet water probably even just spit and they seem to survive somehow so what I'm suggesting is not really far fetched.
Think outside the box.