Mystery stains in plaster pool

[Brian Malone]

Hi TFP - I recently performed an ascorbic acid treatment on my 20 year-old pool; following the instructions here: Ascorbic Acid Treatment - Further Reading

My pool now looks great - almost like new. I have two corners that still have a slight darkness to them. They have always had a black staining whereas, the main pool had brown stains which have completely disappeared. Any ideas on my two slight dark areas?

 

[ajw22]

Could be a bit of copper staining.

You know how the iron got in your water?

Copper in Pool Water - Further Reading

www.troublefreepool.com

 

[Brian Malone]

I believe it has been leaching in from years of cedar needles that fall in the water during mainly the winter months. And the cedars have 28- 30 years of growth. I used some old school algaecide about 5 yeafs ago to clear some difficult algae. I never really noticed the dark spots when the plaster had the general all over brown stain. Now with the plaster white again, the dark spots in the corner creases stand out. I will have test for copper. Thanks! I just have keep the iron sequestered.

 

[Brian Malone]

I will try out the guidance in TFP copper link you provided. The TFP ascorbic treatment guidance worked beautifully. I just have to get the test kits per the TFP recommendations.

 

[ajw22]

The algaecide s you were using may have had copper in them.

 

[Brian Malone]

Yes, the maximum strength algaecide I used back then definitely had copper listed and it was a dark blue color. It got rid of the stubborn algae! I have read the TFP algae info info and understand the situation. I'll add copper sequetrants and wait until wintertime to do small iterative water exchanges to reduce the dissolve metals. Though I originally signed up on TFP back in 2013, I never really checked out the resources and system until recent. I am a total believer now - my old pool looks great and my maintenance time is sooo much more effective. Thanks for the assistance!