As Mardoo, nope.
It's a sanitizing agent, so it'd be pretty useless if it couldn't even sanitize it's own diluting solution [emoji1]
However, having said that, I believe some water sources that are hard (ie: high in minerals) can be less than ideal as the minerals "consume" the acids in the starsan.
Similarly, alkaline water can neutralize the acids. Generally Aussie water (read: eastern seaboard) is not sufficiently alkaline (or hard) to be a major issue, maybe just add a whisker more starsan syrup to counter the base.