If you use a Water Purity meter and test your home tap water, you will find that the reading can differ wildly even on a daily basis and of course depending on what part of the country you live in. In our part of the world (southern England) 308 parts per million is not uncommon. The ideal however, is '0' parts per million.
We manage to obtain a level of 1 to 8 parts per million on a regular basis due to our methodical and scrupulous testing. If you see a Vodka Luge or Ice sculpture that is a little cloudy or not crystal clear, the water has not been purified.