Hmmm. Sheet method sounds interesting. Thanks for finding the post. My pool store folks are saying to never drain more than 6 inches below the skimmer. They suggest a series of partial refills. I think it would take me the rest of this summer and half of next to replace the percentage of water necessary to get my CYA down to where it needs to be (I'm at cya 90 with 20K gallons). Since I have metal and cya, I really, really want to get some fresh H20 sooner rather than later.
Pool tech did find a little bit of pink behind the light fixture when he removed it. Very small amount, he said. He left me a bottle of Pink Treat, but I'm hesitant to use it because someone on here said it can create a high chlorine demand. That's how all this started, (high chlorine demand after AA treatment and excessive amounts of metal sequestering agent), soooo don't want to go back there again.
I passed the FC loss test, but I'm right on the edge. I lost EXACTLY 1 ppm of FC last night. I read my CC as .3 because the sample almost clears with one drop (I'm using a 25 ml sample for more accuracy right now, so even with the second drop, I'm at .4, still in range). My water is crystal clear. There is no visible mold or algae. Knock wood.
Pink Treat calls for an immediate shock right after you add it. I'd really like to get in the pool this weekend, so I'm not sure whether to treat and shock or wait and see.
As far as the metal issue goes, there is very light staining on the fiberglass steps, and I'm still running with a high FC (7.5) and Ph at 7.4. So metal's still there, but I'm surprised these high FC levels have not made the whole pool dark brown. I may buy one of the iron test kits, not sure which one, to see if it will detect my level. Testing at the pool store has turned up nothing, but the Metal Magic may have been fooling the test. Would like to have a home kit for monitoring.
so I don't believe the tests can TELL you how much iron is sequestered that will be RELEASED if ph gets high, or the sequestering agent wears down, etc.