Pool Stains - What is causing it?

May 24, 2021
8
Dallas, TEXAS
I have around 3 spots with brown stains, that does not come off even when I brush. They are about close to a penny size or less. PB says these stains are from scaling and mineral deposits on top of scales. They are directing me to add BIO-DEX Protect All to clear the scaling, which they think may take some time to clear.

What you all think is causing the stains? How should I address the stains? Just trying to get second opinion to see what the experts here think is the problem.

In addition to this I also have scaling problem on the water line and above around tiles.

Pool Chemistry
I will be working on bringing the CYA little bit low in the next week or two. Right now I have a pretty basic test kit Taylor K-1003, and will soon be investing in a better test kit. Based on TFP method or calculators, I think I need to increase my chlorine usage higher to around 5 ppm.

| 10 months old pool | Pebble Sheen finish|

7/20/2023 Pool test from Leslie's | FC 1.24 | TC 1.34 | pH 7.4 | TA 82* | CH 206 | CYA 76 | Iron 0 | Copper 0.2 | Phosphates 0 | TDS 7000 |
| *TA has been adjusted due to the effect of CYA on tested TA |

 
Last edited:
I'm certainly no expert, but to me it looks like rust. Is it possible rebar is poking through the gunite? You might be able to check this with a magnet. Either way, use vitamin C to help diagnose the stains as outlined in the article.

 
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First thing I would do is obtain either a TF-Series test kit or Taylor K-2006C. The TF kits (link in my signature) are a better value IMO, but 100% your choice. Avoid the pool store products and certainly do not take any actions based on their testing.

As to the stains, do some DIY tests first:
1 - Rub a chlorine tablet or sprinkle some cal-hypo on the stain (organic)
2 - Rub the stain with a Vitamin C tablet (iron). Possibly from underneath (rebar). See if a magnet sticks.
3 - Rub with dry acid (pH Down) (copper).

They look more like either iron or organic/Tannin stains. See if any of those DIY tests make any difference and let us know.
 
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