In the U.S. you probably don't need TDS to be brought down to zero. My water filtration system at home uses reverse osmosis and brings TDS from 150+ to just 20

In the U.S. you probably don't need TDS to be brought down to zero. My water filtration system at home uses reverse osmosis and brings TDS from 150+ to just 20 and the filter lasts more than a year. (Those that bring TDS down to zero might use deionization instead.)