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Thread: Algae stain

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    Krickett's Avatar
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    Algae stain

    Pool Readings:
    FC = 5
    pH = 7.4
    TA = 70 (Just added baking soda to bring it up to 90)
    CH = 250
    CYA = 50

    Background:
    Had pool replastered on June 2007. 10/2007 - 4/2008, covered pool and didn't attend to it over that time. April of 2008, cleaned the pool and kept it clean, except for 1 or 2 algae blooms until 10/2008. 10/2008-6/2009 reduced water level below skimmer several inches, covered pool and didn't attend to it over that time. Finally got it clean after considerable work (Refer to http://www.troublefreepool.com/diary...mp-t15087.html). Since then I have kept it clean except for the occasional algae bloom which I dealt with quickly.

    Problem:
    Because of my actions the pool walls were stained from a couple inches below the skimmer down. The stain color was fairly consistent with a vague green tint. The stain has progressed to the point where the areas that covers over the old water line down several inches have turned dark green. Pictures are below.

    Question:
    I realize that letting it stay so green so long was a mistake and I will be keeping it clean year round from now on. My question is how to best clean the pool walls. I shocked the pool two weeks ago and have been brushing the pool but the stain remains. Algae blooms seem more common. Scrubbing with stainless steel brush has no effect. I also rubbed a puck on it for several seconds with no effect. Using a pumice stone did clean most of it up but I can't use that for the whole thing. Would an acid wash, pressure washing or something else be the best course of action?
    Attached Images Attached Images
    21k gal, plaster IG pool with spa
    Main - 1 skimmer, 1 main drain, 3 returns, Spa - 1 drain, 4 returns
    WhisperFlo Dual Speed WFDS 1.5 HP pump
    S310S 30" sand filter
    Polaris 360 pressure cleaner

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    Mod Squad JohnT's Avatar
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    Re: Algae stain

    If it's from algae, raising your chlorine to shock level and holding it there should fade it.
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    20K Gallon 20X36 Vinyl Inground
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    Krickett's Avatar
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    Re: Algae stain

    I pretty sure it is from algae. It looks like algae with the same color. I have added chlorine to the shock level and left it there for close to a week with no change.
    21k gal, plaster IG pool with spa
    Main - 1 skimmer, 1 main drain, 3 returns, Spa - 1 drain, 4 returns
    WhisperFlo Dual Speed WFDS 1.5 HP pump
    S310S 30" sand filter
    Polaris 360 pressure cleaner

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    Re: Algae stain

    Could it be metal staining? I am certainly no expert but might be worth holding a Vit C tablet to it to see what happens.
    Plano, TX
    25,000 Gallons, Plaster, DE Filter, No SWG

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    Krickett's Avatar
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    Re: Algae stain

    Tried that last year with the original staining. It is not from metal.
    21k gal, plaster IG pool with spa
    Main - 1 skimmer, 1 main drain, 3 returns, Spa - 1 drain, 4 returns
    WhisperFlo Dual Speed WFDS 1.5 HP pump
    S310S 30" sand filter
    Polaris 360 pressure cleaner

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    Re: Algae stain

    Quote Originally Posted by Krickett
    I pretty sure it is from algae. It looks like algae with the same color. I have added chlorine to the shock level and left it there for close to a week with no change.
    What FC did you bring your pool to when you shocked?

    When it comes to stains, it's basically either metal or organic. Since the vitamin C test was negative as you say it was, then that leaves us with organic staining. Organic staining will go away in time with chlorination at normal levels. Raising the FC to shock level will help it disappear more quickly, but either way, it may take some time and patience on your part.

    ETA: Does the stained area feel rough to the touch?
    10K gallon IG gunite with waterfall; Pentair CC320P filter; WhisperFlo 2 HP pump
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    Krickett's Avatar
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    Re: Algae stain

    FC exceeded 16. I tried to keep it around 18 which I did for about a week. The stain does not feel rough. It feels like the none stained plaster. Keeping FC levels high may fade it but how can I get rid of it all together? Would pressure washing it and then scrubbing it with bleach be the best way or an acid wash?
    21k gal, plaster IG pool with spa
    Main - 1 skimmer, 1 main drain, 3 returns, Spa - 1 drain, 4 returns
    WhisperFlo Dual Speed WFDS 1.5 HP pump
    S310S 30" sand filter
    Polaris 360 pressure cleaner

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    Mod Squad JohnT's Avatar
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    Re: Algae stain

    Your statement that "Algae blooms seem more common." makes me wonder. If your chlorine is right, you won't get algae. If the stains are green, your chlorine level hasn't been high enough for long enough. With a plaster pool, you can go as high as you want for chlorine, so I'd knock the heck out of it.
    TFP Moderator
    20K Gallon 20X36 Vinyl Inground
    Hayward S244T Sand Filter with 1HP Whisperflo Pump. Liquidator C-201 and Solar Heat

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    Re: Algae stain

    With CYA 50, the Chlorine/CYA Chart says to use a shock level of 20. Check it a couple times a day if you can. Also lots of brushing.
    --paulr
    BBB "Intermediate Swimmer"
    IG plaster pool 18.5K gal, Hayward Pro-Grid DE filter, 3/4 HP Hydramax II; Polaris 380, 3/4 HP booster
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    Krickett's Avatar
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    Re: Algae stain

    According to the pool calculator http://www.poolcalculator.com the shock level is 16 for CYA of 50 so I'm not sure which takes precedence. In any case my numbers were wrong. I was using CYA and calcium from a month ago and adjusted CYA up by 5 with the assumption it had gone up a little but that seems wrong.

    FC = 4
    pH = 7.8 adjusting to 7.4 with acid.(not sure why it went up except other day was in natural light and this reading by florescent)
    TA = 70 adjusting with baking soda (not sure why it is still the same considering how much baking soda was added except that the other day I used an old test kit)
    Calcium = 350
    CYA = 35

    I'm going to bring and hold the shock level to about 25 to ensure I am high enough for about a week to see if it makes any difference.

    I added 22 oz acid and 76 oz of Cal-hypo 73%
    21k gal, plaster IG pool with spa
    Main - 1 skimmer, 1 main drain, 3 returns, Spa - 1 drain, 4 returns
    WhisperFlo Dual Speed WFDS 1.5 HP pump
    S310S 30" sand filter
    Polaris 360 pressure cleaner

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    JasonLion's Avatar
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    Re: Algae stain

    Either shock level works. 16 is good enough, 20 is quicker.

    There is no need to adjust your TA just yet. Get all the problems taken care of and then worry about TA.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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    Krickett's Avatar
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    Re: Algae stain

    I got the pH down to 7.5. I thought I read that for shocking it is better to lower the pH to about 7.2. Is that true? If so, why? I tested chlorine and it was 17.5 so I adjusted it back to 25.
    21k gal, plaster IG pool with spa
    Main - 1 skimmer, 1 main drain, 3 returns, Spa - 1 drain, 4 returns
    WhisperFlo Dual Speed WFDS 1.5 HP pump
    S310S 30" sand filter
    Polaris 360 pressure cleaner

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    JasonLion's Avatar
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    Re: Algae stain

    First, you can't rely on the PH test when the FC level is high. Wait till the FC level is below 10 before adjusting the PH. Second, the PH only really matters for shocking if you don't have any CYA in the water. As soon as you have some CYA in the water, the PH anywhere in the normal range only makes a small difference to shocking.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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    Re: Algae stain

    ------
    Last edited by NewHomeowner; 05-31-2016 at 10:42 AM. Reason: Started own thread. Wish to delete post.
    48,000 IG Gunite - Pool built 1999
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