John's Copper water quality test strips combine a wide range of detection of free copper in water with no interference from Iron and can be used in water with a wide range of pH. These water quality test strips are safe and easy to use for fast, accurate results within the ranges of 0 to 2 ppm (mg/L), which are typical copper levels found in tap, well, and stream water. The unique, patented test strip allows for low level detection without sacrificing accuracy.