Looking for advise from the forum chem experts on identifying metal stain I’ve been dealing with for a couple of years. I have large brownish stains mostly in deep end around the bottom drain. At first I thought they were organic stains resulting from the accumulation of earthworms that always seem to find their way into the pool during the winterization period. However they did not fade with chlorine and I found I can remove them by placing a sock with vitamin C powder on the stains. The vitamin C seems to oxidize the stain and it first turns very dark purplish before eventually fading completely away.
Gradually the stains return to the exact same location. I have not been keeping proper level of sequestering agent to keep metals in suspension and instead been content repeatedly spot treating with low cost AA powder. Because the AA removed the stains I have assumed them to be Iron. I did have a rusted pressure gauge on top of my CCP filter that I replaced last year which may have been the source.
Planning to do AA treatment this spring and follow with proper Sequestering agent protocol, but have a couple questions.
1. Is it normal for iron stains to turn from brown to dark purple before fading? I haven’t seen this described in anything I have read on the topic.
2. I understand the concept that the AA lifts the metal from the plaster and if the ions are not sequestered or removed, the metal will precipitate back into the pool plaster. However, why would this happen in the exact same location vs randomly recurring in different locations?
Gradually the stains return to the exact same location. I have not been keeping proper level of sequestering agent to keep metals in suspension and instead been content repeatedly spot treating with low cost AA powder. Because the AA removed the stains I have assumed them to be Iron. I did have a rusted pressure gauge on top of my CCP filter that I replaced last year which may have been the source.
Planning to do AA treatment this spring and follow with proper Sequestering agent protocol, but have a couple questions.
1. Is it normal for iron stains to turn from brown to dark purple before fading? I haven’t seen this described in anything I have read on the topic.
2. I understand the concept that the AA lifts the metal from the plaster and if the ions are not sequestered or removed, the metal will precipitate back into the pool plaster. However, why would this happen in the exact same location vs randomly recurring in different locations?