Unfortunately, this is probably purely an effect of the pH. Low pH dissolves metal, and keeps it dissolved. Higher pH causes it come back out of the water, as stains or precipitate. The fact that you had to add so much borax indicates that your actual pH was MUCH lower than 6.8.
One question you need to try to answer is, "How did that iron get into the pool?". There are two likely ways: it was in something you put into the pool, OR something has rusted or eroded badly. Is there any place in your pool or piping where the water contacts steel? You reported using utility water, and usually, utility water is NOT high in iron.
Anyhow, you may want to lower your pH back to 7.0, add a liquid stain/scale product, polyquat, keep your chlorine low, AND run your filter 24/7. I'm listing products from Amazon. You can buy from Amazon, or you can use the links to ID what you need locally. If you buy from Amazon, I'd recommend getting the stain/scale product next day, so you have it Friday.
The ascorbic acid stain removal page explains how to do it.
Products for metal control and clean-up:
HEDP is a liquid phosphonate that is pretty chlorine stable, and very good at keeping dissolved metals IN the water, instead of ON your pool surfaces. It can lift recent stains, OR it can be used along side of ascorbic acid, to keep the metals in the water, after the ascorbic acid is consumed by chlorine.Jacks Magic The Pink Stuff 1qt (60% HEDP) @ AmazonUsing polyquat during metal clean up accomplishes two things: it helps kill or prevent algae, letting you run lower chlorine levels, and it is a very good clarifier, that helps you filter out any small metal particles that may form.(Probably available from pool stores, and possibly some big box stores -- but you MUST learn to ID it correctly. See the polyquat page for more info.)
20% KemTek HEDP @ Amazon
Kem-Tek 60% polyquat @ AmazonAscorbic acid (Vitamin C) can be used to remove copper and iron stains from pool surfaces, and put the metal BACK into your pool water. (Not likely to be available locally, except as Vitamin pills.)
Nava 60% polyquat @ Amazon
Ascorbic Acid Powder @ AmazonThe CuLator product is a special patented plastic material, contained in a bag that goes into the skimmer, that can slowly take metals OUT of your pool water. We think it works, and have some evidence that it does, but not proof yet. (Not likely to be available locally.)
Ascorbic Acid Vitamin C Powder USP Pharma Grade 11 Lbs @ Amazon1 ppm Culator @ Amazon
1.5 ppm Culator sold by Amazon, shipped from Periodic
4 ppm Culator sold by Amazon, shipped from Periodic
Poolmaster 16242 Poolmaster Skimmer Basket Liner @ Amazon (to protect CuLator from being damaged by scum)


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