If you are not looking to spend much on vodka you can filter Popov or Fleischman's four or five times and improve the taste greatly while significantly reducing hangover potential. You won't really be improving the flavor, so you may not be able to turn the cheap stuff in Grey Goose, but at least you'll get something cheap and drinkable. Works for gin too. When I get to the end of the useful life of a water filter I always do this - not advisable to put vodka through your Berkey before you are ready to replace it. TRUST ME!