As a sanitizer copper ionatzation kills far more types of bacteria than chlorine. I have used it with several customers. We put several friends / customers on a ion system that creates copper sulfate. It works incredibly well, but it is also very difficult to keep up. you need to have between 0.2 and 0.5 ppm of copper. If you get to much copper in the water (over 1.0 ppm) the entire spa will be stained green. Hair and bathing suits will also be stained green. I have several customers that swear by it.