Water from the grocery store machine.

I get all my drinking/cooking water from the machine in the grocery store. While I'm filling up my 5 gal. plastic water bottles I read on the label that it's basically filtered, reverse osmosis water (as I expected). But the final step is what they call "UV sterilization" which was probably defined by the marketing guys. I'm just thinking, if I sanitized my container first, this grocery store water is probably just as good for adding to wort after the boil as my current method using boiled then refrigerated water.

Reverse Osmosis water is fine for top-off. I'm just curious what this "UV Sterilization" is. I don't think it would be a problem but you never know. Maybe you can get a URL form the dispenser and check it out on their website?

UV sanitation is done with a high powered UV light . The water passes the light in a clear tube or vessel and the high UV kills bacteria they sell small units for home and camping. It doesn't effect the water at all .

It is probably just fine for topping up. I'd only be worried that someone touched the nozzle after the UV sterilization.