The SunPurity is the same chemically as the Nature2 for spas. The difference is the shape. The SunPurity is designed to fit into the Sundance brominator.
The product sold as Nature 2 for spas is not the same as the product sold by the same name for pools. The pool product distributes both silver and copper ions into the water and is quite effective in sanitation in conjuction with small doses of chlorine, e.g. 0.5 ppm continuously. For reasons that the manufacturer (Zodiac Pool Care, Inc. - see site at
www.nature2.com) is unwilling to discuss, the spa product only distributes silver ions into water and is much less effective in sanitation than the pool product with the same name.
Details of the failure of the Nature2 spa product to perform as a sanitizer as advertised can be found on the Roberts Hot Tubs site at
http://www.rhtubs.com/cgi-bin/bbs/config.plSee the Vermonter and Northman (two expert microbiologists) posts and info within the FAQ portion of the site. Nevertheless, Northman strongly recommends that the Nature 2 spa product be used for its ability to soften spa water and allow for some sanitation when the chlorine level drops.
I have personally contacted the Zodiac manufacturer and received some information on a few scientific studies of the spa Nature 2 product. The info is non-conclusive about its action as a sanitizer. However, they quote study results that appear to show effectiveness against some microbes, without studying any real situations with the kinds of microbial contaminants that all spas have. It is also clear that the manufacturer is unwilling to explain why they made the decision to not include the copper ions,which appears to be the key to any real effectiveness in combination with silver ions.
So, this is a product that may provide some benefits, but you absolutely cannot count on it as a sanitizer. It does soften spa water and gives water a silky feel and provide at least some residual sanitation. For about $22-25, its certainly worth a try.
Electro