Bests & Worsts Reviews from Amazon

I ordered the TDS-4 after reading several reviews on it and other products as well as comparing the specs to its rivals. I read all the specs for each tester I found and it came down to this TDS-4 and the TDS-EZ. The determining factors were its accuracy and ATC. The TDS-4 has a stated accuracy of +/- 2% as opposed to the +/- 3% of the TDS-EZ. The TDS-4 has ATC (Automatic Temperature Compensation) which comes in handy since water can be different temps. Each had the same hold and auto-off function and read in 1 ppm for the first 999 and 10 ppm for 1000 - 9990. One disappointment I had with the TDS-4 was that it didn't have a "How pure is your water?" chart on the back like the TDS-EZ. It's not hard to remember what's on the TDS-EZ chart, but would be a nice-to-have. Instead I just remember that 0 to 50 is what my RO system should be at, 50 to 100 are carbon filters, 100 to 200 is hard water, 200 to 400 is average tap water (200 to 300 being marginally acceptable drinking water), and that 500 is the EPA's max level it should be (Source: TDS-EZ chart). I originally ordered the TDS-4 to test our new RO (reverse osmosis) under counter filtration system (Watts Premier WP-4V). Now for my experience with the TDS-4, when I received the unit from Amazon I immediately tested my RO system first (29 ppm), then my tap (251 ppm), and finally RO water from a local watershop (2 ppm). My RO system was in mid-range of the 0 to 50 acceptable for RO systems, my tap was in the mid-range of acceptable tap levels of 200 to 300, and the water from the watershop was almost pure water. I'm pleased with my RO system compared to the watershop since they have huge filtration systems and the WP-4V takes up less than half of my cabinet under the sink; although, I do wish they tasted identical, the WP-4V tastes good, just not perfect like that from the watershop. I did another test at my employer who a filter on the drinking water, the result was 221 ppm, I knew it was bad, but expected better because of the filter which I don't know what kind of filter it is. Needless to say I'm bringing in my own water for now on since the water from their tap was 240 ppm. I ordered the TDS-4 from Amazon Prime and received it in 2 days in perfect condition. I would definitely recommend this to those who want an estimate of what the level of TDS is in their water, it will also come in handy to show the life of our RO filters.