Waterbear, Pamsel had put in a lot of sequesterant, that is why I am having trouble thinking it is copper - although the first set of pictures she has here (the last two) the water looks clear green, which does look more like copper coloring the water. But she is losing chlorine fast, and the stuff in the last picture she posted looks more like algae than anything. My thought is that if she lowers the ph and alkalinity, the chlorine will be more effective in killing the algae, plus you know high chlorine levels and high chlorine are what make metals fall out of suspension - there doesn't seem to be any staining on the steps in the first set of pictures. This is a very confusing case - maybe you can help - you are great with the chemistry - what is the difference between a chelating product and a sequestering product? I also think there may be a filtering problem - because there isn't much coming out with the backwash - and the pressure is at 40, when it ususally is aroung 18. Could channeling be the problem? You can read Pamsels other posts in the metals forum, and maybe you have some ideas that can help. Thanks!