I live in G-burg and the nitrates in the tap are not detectable with eithre Salifert or API test kits, so I'm wondering, did you test it right from the fawcett and get different results? (same goes for phosphate).
Until you get an RO unit, you could do what I do. The Safeway by Lakeforest Mall has a fill-it-yourself purified water machine.... its only 39 cents a gallon when you use your own containers, which is practically nothing (to use their containers, it's 64 cents but you would only have to pay that the first time to get the jugs, and even then, it's cheaper than getting water off the shelf. There's a brand name on the machiens, which I think is Glacier but I really am not sure.
I would skip on the canister filter. I was using one until a few weeks ago and kept having to open it to clean it up to keep it from holding nitrate. Ha, now the hoses are being used for my uv sterilizer.
With the plain tap water, in addition to other things, I would be concerned about flouride. I didn't know it was being added to the water until recently when I read up on all kinds of health problems people have been having from it.