Well, as I said, I've lived in recycled water area for over a decade, so I think I can say that I'm well aware of the difference. I was also aware of the fact that they do top it up with regular water too.

But just fill up two 20L white buckets... one with recycled water, one with regular water, and then try and say that you can't tell the difference. Hint, if you can'te tell, you should probably be handing in your drivers license as you're eyes are too far gone for you to be safely driving your car