Puzzling "stain"

In January a service tech added a copper-based algaecide that he has used with great success for many years. The pools had cya readings around 100 and the pool temperatures were 58 degrees - all other chemistry was within range. A few pools developed a lavender stain (not purple or pink but a little of both) throughout the pool. At the returns and skimmer the stain could be reduced with heavy rubbing.Treatments with acid-based stain removers has had limited efficacy. Spot treatment with a mixture of granular acids had no effect.Any suggestions would be greatly appreciated.

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  • Bruce,
    I agree with you that a chlorine bath is needed to kill algae before replastering, and I see no problem with bonding as long as a good rinsing with water is performed following the chlorine bath. That is the same concern I had when doing an "acid bath" for preparing for a replaster job 30 years ago when I was in the plastering business. There was a residue on the plaster that needed to be removed.
  • The stains you have are high levels of copper. I have seen purple even in the grout of the tile. When adding copper based algicides you must know the saturation index and exact chlorine level. Most of the time I have seen this with chlorine levels over 5 and pools on the scale side of the saturation index. What surface do you have on these pools?
  • Oh Kim there you are. My reason for uncertainty was : what effect, if any, would a chlorine bath have on possible failure of new plaster to bond. Knew you would chime in eventually. LoL We've done many things in years past that you guys are finding were not the best methods. Keep up the good work and flow of info.
  • Hey Bruce,
    If you were referring to me, why would I be opposed to your suggestion and position? I agree with your assessment.
  • Charlie, the short answer is...no.

    Back when we all walked around in Pilgrim suits, agood power wash followed by bleach poored on the walls was standard treatment prior to replaster. I know I'm may be causing Kim some discomfort by recommending this, but you must kill and remove black algae before proceding. In 24 hrs. the chlorine should be gone and other treatments can be applied. If you have ever painted a pool you will be familiar with the proper preparation of the surface. You know, TSP, acid, TSP, But no matter what you do, remove the algae first, then kill the "roots" before putting anything else on the suface.
  • Hi Bruce,
    I've noticed that you have posted before about black algae. Do you know about putting bond kote under a marble dusting as being a very effective way of redoing a pool that has had black algae so that it won't come through again. My marble duster would normally do that (which would be relatively inexpensive) but he now wants paint the pool with some other product that he says is new that he guarantees will not let the algae through the new marble dust, only thing is - it costs $1,600 before we even start the marble dust.
    just wondered if you had any knowledge of it.
    am going to post something now - thanks,
    Charlie

    Bruce Hudson said:
    Gotta be carefull with those copper algicides for sure. Years ago I left a bottle of copper algicide with a lady with directions on how to add it for treating mustard algae. If memory serves, it was 3 oz/day for 3 days......You know the thought process, if 3 oz. is good, 6 is better, and so on. When I returned a week later to service the pool, the instrutions called for shocking the pool, which I did.....RuhRoh. As she looked on with blind faith, the bottom of her pool turned the most awesome colors......green, blue-green, and under the heaviest concentration of cal-hypo, purple!!! That's when she confessed to the heavier doses of algicide and in full panic mode I set about trying to mitigate the damage.
    I added 1 gal. of acid (12,000 gal. pool) and 1 qt. of stain control, which I had to purchase from a nearby pool store as I was about 15 miles from our shop. Then I started scrubbing. The stain lightened considerably within an hour and a week later was barely noticable.
    As you might have guessed, I now do not use copper except in the most extreme of cases. Quat, Poly-quat, Bromides are much more forgiving on the route tech and copper/silver should be reserved for special cases. In most cases, Mustard algae can be effectively controlled by paying strict attention to maintaining a pH of 7.4 with cl. @ 3-5 ppm without the use of algicides.
    As Luke said, Jack's is a great group to consult for staining issues.
  • Gotta be carefull with those copper algicides for sure. Years ago I left a bottle of copper algicide with a lady with directions on how to add it for treating mustard algae. If memory serves, it was 3 oz/day for 3 days......You know the thought process, if 3 oz. is good, 6 is better, and so on. When I returned a week later to service the pool, the instrutions called for shocking the pool, which I did.....RuhRoh. As she looked on with blind faith, the bottom of her pool turned the most awesome colors......green, blue-green, and under the heaviest concentration of cal-hypo, purple!!! That's when she confessed to the heavier doses of algicide and in full panic mode I set about trying to mitigate the damage.
    I added 1 gal. of acid (12,000 gal. pool) and 1 qt. of stain control, which I had to purchase from a nearby pool store as I was about 15 miles from our shop. Then I started scrubbing. The stain lightened considerably within an hour and a week later was barely noticable.
    As you might have guessed, I now do not use copper except in the most extreme of cases. Quat, Poly-quat, Bromides are much more forgiving on the route tech and copper/silver should be reserved for special cases. In most cases, Mustard algae can be effectively controlled by paying strict attention to maintaining a pH of 7.4 with cl. @ 3-5 ppm without the use of algicides.
    As Luke said, Jack's is a great group to consult for staining issues.
  • Found this web site--Maybe it can help. Discusses Lavender.

    http://www.poolspaforum.com/forum/lofiversion/index.php?t212.html
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