Actually, I asked that question myself on this forum at least once, and got no responses.<br><br>I know that boaters and RV folks use commercial products of some sort to keep the freshwater systems aboard from freezing up in the winter.. but my impression is that, while it's supposed to be "non-toxic", they still try to flush it before use.<br><br>Vodka works to some degree, but may have unintended consequences. :-)<br>