tl;dr; I sanitized my mash pot, fermenter, and everything with water. Is it ruined?
I'm two days into fermentation of a high gravity imperial stout, and the yeast is burping nicely. Due to a mix up between my wife and I, I just discovered that the star san spray bottle I used to sanitize everything was actually just water. Certainly this is not ideal, but is it dangerous? Should I let my brew ferment and see how it tastes, or give up now and throw it out?
Your brew is fine. If there's a problem it will be obvious when you taste it. Relax.
As long as your gear was (at least reasonably) clean chances of an infection making the brew dangerous is absolutely tiny. Botulism or something actually nasty is very unlikely.
Specific brewing strains of yeast are relatively very aggressive and will tend to out compete some random wild yeast or bacteria and kill it off with ethanol a few days in. So as long as it is bubbling away the yeast is doing its job. Remember in olden times fermenting was a way to make and keep liquids safe to drink.
Now there might be some affect on the taste and you can only judge this once it's done. You could consider drawing a small sample to check gravity and progress and tasting that as well. Just remember a partially fermented brew will taste kind of weird at the best. Anyway, in conclusion, wait and see if you like how it tastes in the end! It might end up a tiny bit off or different than you wanted but still nice anyway.
