Even with a massive house filtration system (removes almost all DOS, chemicals etc.). I still have a high nitrate reading coming out of the taps. I'd like to add a r/o,di unit to remove this; as 1: I don't have an LFS that is less than 60 miles away, and 2: After testing the water from the r/o,di units at most grocery stores nearby, they aren't all that great (must not be changing out the filters as they should be). I'd like some recommendations on a brand that is 1: easy to use, and 2: won't break the bank, but will get the job done. Again, nitrates seem to be the only problem left, DOS and most other problems have been eliminated by the main filtration. Thanks.