if you live where theres hard water it woulds benefit you but if you have soft water you probably would be wasting you money i live in the uk so have hard water i would like to use a RO filter but its not top of my list of things to get to enhance my growing power
unless you have water that needs filtering before you drink it wouldnt spend a fortune on purifying your water it would benefit you, probably jus not that much
they basically take out all impurities leaving you with near enough pure hydrogen and oxygen so you may need to add some stuff to it for ya plants to grow better