So I tested this product in 2011 - see here culator-ready-to-test-t33989.html At that time I never had the pool water tested for metals, although I was seeing brownish staining that readily disappeared with a vitamin c tablet.
I'm still getting metal staining that easily lifts off with vitamin c. The pool store near me has a new water testing machine - http://www.lamotte.com/waterlink_spin.html (the old machine was the same company but not the spin type just the regular Waterlink). I think someone here advised that this Waterlink machine was fairly accurate.
So..test before CUlater showed 0.5 copper, test after showed 0.3 (using the Pool store Waterlink Spin). Iron is 0.1 today but I can't remember what it was before (and can't find the paperwork either - will check and see if pool store has it on file in computer).
The bag looked slightly blue so I cut it open. In my 2011 test the power inside stayed white...this is the powder in my new test.
Now the only thing I don't know is what colour the powder was when the bag was new. In 2011 the powder was white when I cut the bag open after using it. I don't know why the manufacturer would now be using blue coloured powder.?? I'm throwing a new bag in tonight and was thinking about opening it to see the colour and then sewing it shut before using it. I know the new copper level is 0.3.
By the way, the bag was in for a couple weeks at least - maybe closer to three weeks. I should have kept better track of how long it was in the water.