I just use drinking water from the grocery store 1 dollar a gallon! It runs between 50 - 125 ppm . My tap water is horrible 580 ppm !! Those water filters in front of a lot of stores works , but I'm not too happy with sitting there filtering jugs of water to save 2 bucks ! RO units are either very slow or very expensive . Also you can get a rain water collection barrel and catch rain water ! Thats free ! Make sure that whatever you use make sure you add your nutes THAN ph your water! Since I started using bottled water my ph problems disapeared !!