Unidentified stains

Ugotabkdin

Member
May 12, 2016
12
Sacramento, CA
Pool Size
16850
Surface
Plaster
Chlorine
Liquid Chlorine
Recently moved into house with a pool (I owned a pool previously so am not a total newbie). The plaster is worse for wear and has lots of staining. We plan on replastering, but have to put that off for now. In the meantime, I haven't been able to confirm what these stains are. See pics. I suspect these stains have been there for a few years.

I've applied tried SLAMing the pool, also applied Cal Hypo directly to brown stains, and don't think there has been any change. I've also done ascorbic acid test (on the stains I can reach on the steps), no effect.

The pool tends to get a lot of organic matter in it from the yard (working to address that), and I learned from original owner that she had had algae problems. So my first instinct was that it is algae or organic matter stains, but wouldn't I have seen improvement from SLAMing pool?


Last test results:
FC 14
TA 110
PH 7.7
CH 250
CYA 60

Thanks!
 

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Last edited:

JamesW

TFP Expert
Mar 2, 2011
23,942
I would say that it's a combination of scale, copper and iron. Maybe some silver if you have an ionizer or if any silver algaecide was ever added.
 
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JoyfulNoise

TFP Expert
Platinum Supporter
May 23, 2015
17,706
Tucson, AZ
Pool Size
16000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
Agree with @JamesW. Most likely “dirty” calcium scale. See if you can apply some dry acid granules loaded in a nylon over the stain for a few minutes to see if it changes. Or, rub a trichlor puck over it fir a few minutes. Trichlor pucks are acidic and highly chlorinated. Cal-hypo is very alkaline and will not affect scale.
 
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JoyfulNoise

TFP Expert
Platinum Supporter
May 23, 2015
17,706
Tucson, AZ
Pool Size
16000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
If that is all correct, what is best course of action?

Replastering ultimately .... in the short term, a zero alkalinity treatment might work but only if you can protect your equipment pad from highly acidic water.
 
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JamesW

TFP Expert
Mar 2, 2011
23,942
Sulfamic acid might work, but that creates its own problems.

Jack's #2 copper and scale product is sulfamic acid.

Sulfamic acid will lock up the chlorine for months.

So, be aware of that.

You just use total chlorine instead of free chlorine until it goes away.