Vitamin C made stains lighter, but much larger

[redmenace20v]

I have many tiny black iron stains from a contractor using rusty scaffolding too close to the pool, despite my many warnings about prep.

I dropped vitamin c tablets on the small black spots and they seemed to lighten but there are now larger brown discoloration surrounding them.

Does this mean it’s working and I need to add more?

Photo attached, this is plaster.

 

[redmenace20v]

 

[Texas Splash]

Normally Vitamin C tabs will have a distinct (positive) impact on iron. Seems a bit odd to me. With a rusty scaffold nearby I would assume iron as well, but perhaps there's another metal involved. Curious, do you happen to have any pH Down (dry acid) granules handy? If not, you might consider a metals test kit like Jack's Magic Stain ID.

 

[JamesW]

Typically a reaction to copper.

Can you pull the filter cartridge and show that?

 

[redmenace20v]

Normally Vitamin C tabs will have a distinct (positive) impact on iron. Seems a bit odd to me. With a rusty scaffold nearby I would assume iron as well, but perhaps there's another metal involved. Curious, do you happen to have any pH Down (dry acid) granules handy? If not, you might consider a metals test kit like Jack's Magic Stain ID.

Thanks, I will try the metal test kit and report back

 

[redmenace20v]

Typically a reaction to copper.

Can you pull the filter cartridge and show that?

@JamesW Thanks for your response. I spent a couple hours reading every related post on this forum, and other forums/sites. I did not see my any posts that indicated this would be a reaction to copper. From my research, reaction to copper makes the stain darker and more prominent, not lighter and larger. It’s possible I missed some threads - are you able to share any so I can correct my understanding.

 

[JamesW]

I suspect that the iron stains probably disappeared and copper stains happened where the vitamin C sat.

Try a Vitamin C on a spot with no stain.

Can you pull the filter cartridge and show that?

 

[redmenace20v]

I suspect that the iron stains probably disappeared and copper stains happened where the vitamin C sat.

Try a Vitamin C on a spot with no stain.

Can you pull the filter cartridge and show that?

Gotcha, that could make sense, thanks for clearing that up. I’ll pull it and post when I’m able to, and try vitamin c in a spot with no stain.

 

[redmenace20v]

I suspect that the iron stains probably disappeared and copper stains happened where the vitamin C sat.

Try a Vitamin C on a spot with no stain.

Can you pull the filter cartridge and show that?

Before cleaning and after;

 

[redmenace20v]

I suspect that the iron stains probably disappeared and copper stains happened where the vitamin C sat.

Try a Vitamin C on a spot with no stain.

Can you pull the filter cartridge and show that?

funny thing is, I went away for a few days and came back and the larger stains are gone. The small dark ones I tried to treat are still there but do seem lighter.

 

[JamesW]

I don't really see signs of copper in the filter.

With a heater, you will always have some copper, but hopefully the levels are not high enough to be a problem.

 

[JamesW]

There are several metals that can cause stains like iron, copper, manganese, silver etc.

There is no clear indication of exactly what caused the reaction.

It might have been organics from some type of organic debris.

 

[Texas Splash]

Curious...... based on your first post we went straight to the metals scenario because of the scaffolding. Since the stains have since lightened or gone away completely, it got me to wondering if any of the spots could've ben caused by something organic falling onto the steps. Do you get tree debris like seeds, acorns, etc there by chance?

 

[redmenace20v]

Curious...... based on your first post we went straight to the metals scenario because of the scaffolding. Since the stains have since lightened or gone away completely, it got me to wondering if any of the spots could've ben caused by something organic falling onto the steps. Do you get tree debris like seeds, acorns, etc there by chance?

The small dark black stains have been there for months and only lightened (and temporarily enlarged) when I left vitamin c tablets on top of them.

The pool cage has been open near there, and still is, but I am really not thinking organics because of the scaffolding timing. I keep my chlorine at the high end based on CYA, and it almost never dips below half that.

I guess I could try to rub a pick on it but I’m leaning towards continuing absorbic acid treatment.