Thank you Waterbear for your chemistry lesson!!! I was under the impression that you could filter out the metals once they were binded on the sequestering agent - That's what I was told, and why I had to keep the pump running. But maybe it was so that it would stain the filter instead of the pool? I have successfully kept the stains away after using the treatmet without draining the water from the pool. I am still trying to figure out where metals get in my pool, and why sometimes I get staining and other times I don't., and it seems that I am not alone in this! I can get the stains off, but can't figure out how to prevent them yet. Is the solution to always keep enough sequestering agent in the pool, and keep the filter running 24/7? What do you think???