I bought mine at Fred Meyer. Only $29.99. The TDS meter that came with it does NOT have a digital readout. Instead, it has a "light" at the top. I'm guessing that if the light comes on , you have bad water, no light, good water. Not sure. This website doesn't even discuss the TDS meter with no readout, so I'm not sure how it works.

I read that ion exchange systems are supposed to be good for filtering nitrates, but not sure if this one does. I bought it to see if it would filter nitrates.