Rust spots turned black with vitamin C

[NoSnow4me]

Hi,

I've had my pool for about a year (it's ten years old), and finally decided to deal with what I believed are rust stains on the bottom. My chems always test perfect by Leslie's Pool, but it wasn't maintained very well by previous owners.

I scrubbed some of the spots off with an abrasive thingamabob that the pool place recommended. It worked in the shallow end, but I couldn't get enough leverage in the deep end to make any progress. Today I tried putting a few vitamin C tablets on a few of the worst spots, and they turned black without diminishing in size. Does that give any of you an indication of what I'm fighting? Any advice would be greatly appreciated.

Thanks,

Dan

 

[Swampwoman]

Welcome, Dan.
Elsewhere on this forum over the years I have heard of this happening and of it being an indication of oxidizing copper. In some cases, the black has later lifted with AA, in others, the stains became rise, and tougher to address. Do you use Algaecides with copper? Do you have a heater, and is there any chance it has corrode? Alternately, and more rarely, I understand this can occasionally happen with iron in a compound stain -- are you on well water?

Since the bit c (Ascorbic Acid) turned the stain black, I would suggest you consider purchasing Jack's Stain ID kit to be certain you know what you're dealing with, and once identified treat accordingly with Jack's products that specifically target different types of stains. Copper is more wiley to treat than, for example, iron, which reliably responds beautifully to AA.

But let me add that if you have metals/stains, and you plan to treat, you ar flying blind to rely on pool store testing.While not directly related to your issue in that the main kit doesn't test metals, having your own recommended test kit would give you the precision to manage metals and staining - we recommend only the TFT100 or Taylor 2006 specifically, available at http://www.tfttestkits.net

For example, stain treatments generally only work well in temporary/deliberate low chlorine environments. Some metal sequestrants (eg metal magic) require a ph above 7.5 for treatment, whie others (eg Jack's Magic) require dropping ph to 7.2 to work right. In general, those with metals in the water benefit from maintaining a lower ph.

Understanding side effects from sequestrant such as temporary clouding (from excess calcium and or underpowered filtration) require the ability to identify whether you have nascent (start of but not visible) algae or if its the result of sequestrant...this you can only confirm by doing an overnight chlorine loss test at a higher FC, again only possible with a drop kit.

These reasons, and others, are why I find it difficult to give any advice about stain treatment to those who rely on pool store testing. Too many unintended consequences

So I hope as a new member of TFP, you will first consider getting a kit to take control of your own testing parameters and be in a better position to get good guidance for successful remedy

Hope tat gives you a starting point. It would be helpful if you posted test results and pictures of you stains. Best wishes!

 

[NoSnow4me]

Thank you for the advice, Swampwoman.

I don't have a heater. I am on well water, but it rains enough to where it is very rare that I have to add water from the tap. I don't think I've added water since around March or so. Even when I do, the water goes through a whole-house reverse osmosis system, so is supposed to be extremely pure.

I will look into the test kit. I have been doing my own chemical testing, but just with a basic set I got at Home Depot. I occasionally have the pool shop test it just to be sure my results still agree with theirs. The water is always perfectly clear, so hopefully that means I'm doing a decent job for the most part, but it looks like the kits you recommended provide a lot more information than I can get with mine.

To update, after the spots turned black, they faded over the course of several days, and many disappeared altogether. In the meantime, some new ones have appeared.

The pool shop guy suggested that perhaps I have a piece of a screw from my aging pool cage on the bottom, and it's getting dragged around when the pump circulates the water, spreading rust spots wherever it settles. I've vacuumed it out several times hoping he was right, but can't tell at this point if it's helping.

 

[gwegan]

The stains are only on the bottom of the pool?

Do you have a pool sweep? Have you carefully sweep the pool looking for foreign matter?

I like the pool guys theory. iTs means something that the stains are distributed as they are yet are only on the bottom.

But I would do some more aspirin testing and frankly get Jack's Magic Stain Id kit. Its cheap but takes some time to do correctly.

 

[JamesW]

That turquoise color looks like copper staining. Can you post an overall picture?