I do not pretend to understand the science behind the foot bath. Somehow, the positive and negatively charged water flow through your body and acts as a magnat (how do you spell that?) to stuff that is floating around not doing anything good. Your body is made of what, 90% water? Anyways, there are color charts that tell you what is coming out. It is a leap of faith that they have scientifically evaluated the substances coming out and are telling you the truth. I get a lot of black flecks and the color of the water is black when I am done and the metallic smell is overpowering! I get other colors too but that is the most prevalent. I noticed today that while I felt great yesterday after doing it, I feel extra tired and weak today. I guess it taxes your body somewhat which is why they say not to do it too often- I am doing it every three days. Eventually, the water is supposed to run clear after the 30 minute treatment and them you know you do not have a lot of junk left. Be well!