Review on Extech FL700 Fluoride Meter by Frank Tyrance

I rarely write reviews, but I do it here. Hope this helps someone. The only reason it even gets 2 stars is because of the cast. svc from the manufacturer at least tries to be useful. They even went so far as to send me a new unit for free after emailing for 6 weeks trying to fix the problem. In the end the problem was not solved and I am convinced that the product design is not perfect. I have private well water that is high in fluoride (5ppm). I have installed a fairly sophisticated fluoride filtration system (in water among other things) and bought this FL700 to monitor the condition of the filter over time to know when to change the media. Anyway the size is a bit confusing but I figured it out. I even bought 1ppm and 10ppm standards for calibration along with post calibration checks. Once calibrated, the meter accurately reads (reasonably) both standards, a distilled water test and a sample from my reverse osmosis system under the sink. However, when I tested my pre-filtered raw well water, the meter continued to read/detect values above its range limit, which is 10ppm (meter reads "OL"). I have a written analysis from an independent lab stating that the original well water is 5.3ppm which is within the FL700 range. Since both meters I received worked the same way, I have to conclude that there is some other "impurity" in my water that is affecting the readings. To prove this, I even spent extra money on a competitor's fluoride tester that uses a different testing method (colorimeter vs. ion level measurement), and these results were consistent with what I already knew or expected. This thing could be good for city water testing monitoring levels of all pollutants, but I'm not even sure I'd trust it then.