Remove metal stains from a plaster in-ground pool

[huumm]

Hi,
I have recently fought back some algea and now my pool has some new rust-like stains. The pool also has some stains from metal coins that the kids from the neighbor throw in that we were not aware until cleaning the pool. I went to a local pool supply store and the owner insisted that he's tried many products but the only one that works for stain removing is Lo-Chlor Multi Stain remover.

http://www.lochlor.com/multi-stain_remover.html

Well, it did not do anything except for making my water from crystal clear to cloudy. I've read the forum and people here recommended vitamin c for stain removing but some where I read that this stuff is only for vinyl and fiberglass pools?

Anyone tried this with their plaster/concrete pool?

Thanks.

[PoolDoc]

Took me awhile, but I found the MSDS, and here's what your looking at:

Sulfamic acid 5329-14-6 20-40 not set not set
Oxalic acid 144-62-7 20-40 1 2
Polybasic organic acid secret 20-40 not set not set
This is a commercial product whose exact ratio of components may vary slightly.
I think it could work, applied directly to a stain. But, if you tossed it in your pool, I believe you'd make a mess. Calcium oxalate would tend to precipitate out, which could explain your cloudiness.

Were you supposed to put this stuff in the, or just on top of a stain? United Chemical used to sell stain spotting bags that were filled with oxalic acid, I believe.

Uh-h, wait found some interesting titbit from their website:

+ After treatment a reduction in pH and/or total alkalinity may occur. If adding a pH adjuster (sodium bicarbonate) then do so very, very slowly.
+ Raising the pH and/or total alkalinity too quickly can cause a cloudy pool as well as re-depositing the stain back on the pool surface
+ Be aware that high levels of chlorine will reduce the effectiveness of Multi-Stain Remover. Ideally, reduce the chlorine level to zero before using this product

Ok, it was supposed to be added to the water . . . at low pH, and ZERO chlorine. (I seem to recall that chlorine and sulfamic acid destroy each other.) Then you had to gradually raise the pH (probably so the filter could remove the calcium oxalate as it formed, and possibly the metals as well).

Sounds like a great recipe for replacing stains with algae.

No, thanks.

[ MSDS & Lochlor source page archived. 20110624 ]

[huumm]

Obviously, it didn't work since I've waited for 24hr since applied the chemical and all I got was the cloudy water. What about the vitamin c stuff? Can I apply it now on my plaster pool or should I do sthing else first ?

Any helps are appreciated.

[waterbear]

Chlorine and oxalic acid also destroy each other and oxalic acid is the ingredient in Pool Stain Treat from United Chemical, which is designed to be added to the pool water just like ascorbic acid, in addition to the Pool Stain Treat spotting bags..
The oxalic acid will reduce (make soluable) metal stains, particularly iron and manganese, while the sufamaic acid is going to remove scale (calcium).

FWIW, I have seen ascorbic acid cloud a pool. It is temporary. Ascorbic acid works on all pool surfaces, it just doesn't work on all types of metal stains. It is great on Iron and manganese and may work on some copper stains but usually does not.