text: can 100% pure water be attained?   yes, assuming you meant to give the significant digits by saying 100%, i.e. 100, not 100.000000000000000000000000%  deionized, double distilled is commonly used.  for certain analytical tests where you need better, there are other techniques to get even purer water.  interestingly, perrier was used by an analytical lab as a standard, because it was so pure.  then the lab noticed they were getting weird results, which turned out to be benzene in the water.  they told perrier, who identified that yes indeed, they were getting some contamination.  they had to do a bunch of work to avoid the contamination source.