Welcome, Big Vic.
I manage metals in my vinyl pool that's on well water. I just want to ask you a few questions to assist you re: staining.
#1 I see you're a new member. Do you have a proper test kit like the ones we reccommend here the TFT100 or the Talor2006 specifically? (These are avail at
TFTestkits.net ) Are you following TFP methods and can you post test results?
-- I ask because there are two things that ultimately play into stain management/or properly following AA treatment guidelines...knowing your ph and knowing accurately your FC. You need to be in a position to test each daily and test strips will not be accurate enough. I recently assisted someone who did an AA treatment flying blind and had unintended consequences, so I wanted to check first
#2 What is your source water?
#3 If you drain and refill, are you aware that with a vinyl liner pool you should not drain completely, and that you should leave at least a foot or more in the shallow end, or more if you have a high water table?
#4 You've said you successfully removed the stains previously with AA...what do you think is the source of your metals? Eg, what was added to your pool?
#5 After using the metal sequestrant, did you slam/shock at all for any reason?
The two metal sequestrants recommended here are Jack's Magic and Metal Magic. After treatment, they need to be maintained. Each recommend not shocking/slamming for a full week after application.
Personally, if you're not on well water, sure there are no metals in your fill water, and if water charges are cheap, in your shoes I'd do a partial drain or two to dilute or eliminate the metals. Copper and iron will stain even at low levels, like .3 ppm, but if you keep your ph around 7.2 consistently and maintain sequestrant you should be fine.
Alternately, there is a treatment I tried last year where instead of doing AA, a member named RavenJim did the Metal Magic sponge test and treated with large doses. It worked for me too, and with MM, the mfg wants the ph at 7.5 or higher, so I found it easier than AA. I will go find the link if you want to read it.
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Here it is
Switching Sequestrate from EDTA to HEDP - Page 2