Thanks so much for the info. I'd really like to get a better understanding, this year, of how metals behave in pools, and responses like yours really help.

I wonder if you could do 3 things:

(1) Tell me how you've been testing. (Do you have a K2006, TFP100 or ?)
(2) Tell me what sequestering agent you used.
(3) Do white bucket tests on both the pool water and your fill water - to see if metals remain in either one.

First two are easy, of course. If you're willing to do bucket tests, here's how it goes:

1. Get a clean white 5 gallon bucket
2. Add 4 gallons of test water (do the pool first, fill water second)
3. Add 1/4 cup each of plain bleach and 1/8 cup of baking soda to the water, and mix till the soda is dissolved.
4. Cover and wait 2 days -- leave the bucket where it won't be moved or disturbed.
5. Check for sediment on the bottom, especially color.
6. Tell me what you find.