Stain Removal - Chlorine Tab and C Tablets Make no Difference

[dbyrne]

Hello All,

First time poster here. I'm in the process of getting my pool back in shape for spring/summer and am having some problems with some stains (see pics). It's approximately a 10,000 gallon salt water, inground, pebbletec pool. The problem I have are these light brown/tan stains that look like sand or or dirt. I've tried chlorine tabs and vitamin c tablets on the stains, in various spots and for various lengths of time, and there have been no changes. I also purchased the stain removal tool where you put acid in the container and let it sit on the stain, and that made no difference either. Based on my research, I'm guessing this is a scaling issue? If it was, though, I would have thought the muriatic acid applied via the stain removal tool would have worked. So, to say the least, I'm a bit perplexed. The pics are from the spa that show the issue I have throughout the pool. Thoughts?

 

[Patrick_B]

Welcome to the forum! :handshake:

Do they feel rough like sand as well? If so, you may be on the right track with scale. To help answer, do you have any recent or historical test results we can look at? Calcium, TA, and pH levels specifically...

 

[duraleigh]

Calcium Scale or iron stains are a good bet.

That said they should both be reactive to the muriatic acid so I am stumped.

What percentage or "baume" was the muriatic you used?

 

[dbyrne]

Thanks for the quick replies. It was pure, 100% acid that I used in in the purity pool spot tool: Stain Removers. Maybe I didn't use the tool correctly? Another consideration, I did have scale buildup at the water line that I've been working on removing. Have most of it removed and plan on lowering the Ph just a tad to help remove it. So I'm guessing scale might be it. To the other question, it is not rough to the touch, at least that I can't tell. How would I test for iron stains; wouldn't the vitamin c have removed it? Thanks again for the input so far.

 

[pooldv]

Welcome to TFP!

Scale is my guess too.

More here
Pool School - Calcium Scaling

and here
Langelier and Calcite Saturation Indices (LSI and CSI)

 

[duraleigh]

Well, it wasn't 100% muriatic.....31% is the strongest you can get typically. Look carefully on that bottle.

How would I test for iron stains; wouldn't the vitamin c have removed it?

Yes, that's the dilemma. The stain should react to the chlorine (organic) or the muriatic (inorganic). There is no in between or exception. I would carefully test again.