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Thread: pool algae/stain help

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    Join Date
    Jun 2014
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    Glastonbury, Ct.
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    6

    pool algae/stain help

    This is going to be a long post, but I've been at it for a long time. I thank any and all in advance for any help they can give.

    I have some algae/stain problems. I'm not sure which they are so I'll post information and photos and hopefully someone will have experienced one of these and resolved it. I've posted photos of all.

    First my values: cya:40, fc:3, cc:1, ch:300, ta:70, ph:7.0

    My fc, ta and ph were adjusted downward for the Jacks Magic tests mentioned below. Normally, I'll keep fc around 4, ta has been 90-100 and ph ~7.4

    I have what looks to me because of characteristics, like 3 different issues:

    First I have 4 spots of what looks like a vague smudge of black. There's no real definition to the shapes. They are dark in color, but not intensely dark, they don't jump out at you.
    I think these are stains. I did 4 Jack's Magic tests on these with no change. I have also used vitamin C with no change.

    Second, I have many spots that I think are exclusively in the spa that are darker and more pronounced. They have a linear and somewhat curved shape - like a parenthesis ")". These all seem to curve in the same form as the curvature of the spa.
    Some have a dark spot about 1/8" in diameter and lighter gray extending away from it with the longest mark measuring about 3". Many are very small 1/8" to 1/2" but they're all over the spa, mainly on the horizontal surfaces, but there are also a few similar marks on vertical surfaces. I think these are an organic growth of unknown type. Rubbing on them with a white cloth yields no color residue. I scraped one with the point/blade of a steak knife, again with no residue. I did remove one of these spots using Muriatic acid - see below. I did the Jacks Magic tests on 4 of these corresponding to the 4 tests in the kit with no change at all. Yes I calibrated my water to be within the JM parameters.

    Third, I have round gray spots the biggest about the size of a nickel spreading throughout the pool itself, but not in the spa that I can see. They are in the shallow and deep ends. I first noticed them on the sunny side (north wall) of the pool, but they have now shown up on all sides as well as the floor of the pool - deep and shallow. I have no clue what these may be. They are unresponsive to hyper-chlorination and brushing. They do not lighten or give off gray residue when brushed. They are individual spots rather than say a colony of spots. I haven't done much with these other than super-chlorination, algaecide and brushing since they are more difficult to reach.

    I own and use a TF-100 test kit for the past 2 years (since these problems started). I have generally kept my recommended levels throughout the past 1 1/2 years while I have been dealing with this - other than when super chlorinating - though there have been a few times when the fc has dipped too low.

    I have maintained super-chlorination at or above shock level for up to 3 weeks at a time, brushing x2 per day. I can segregate my spa from the pool using the valves. I have had my FC in the spa up to 50 for 3 or 4 days, scrubbing x2 per day and had 0 positive results of either elimination or even change.

    I have put vitamin C on the smudge spots with no change.
    I drained the spa, used a chlorine 'puck' and covered every curved mark with the chlorine and then kept the chlorine moist by hose spray for 2 days.
    I have scrubbed the spa marks and applied concentrated algaecide (see Shotglass method photos) and straight bleach on them to no avail.
    I've used Leslies 'black algae algaecide' in the pool while super-chlorinating and scrubbing.
    I've used Poly 60 algaecide while super chlorinating and scrubbing.

    I've had my water tested for metals and it shows a .6 level of copper and a similarly low number for phosphates. I do have something purported to remove the copper and will treat with that after next week, though I don't believe a low level of copper is complicit in these many problems.

    The only thing that did anything is the following:

    I made a 50% mixture of Muriatic acid. I selected one spot of the curved algae (?) on the top step of the spa. I drizzled the mixture onto it and scrubbed, waited a few minutes and did it again, a few minutes later again, for about 15 minutes. This did eliminate the one spot that I chose. This is why I believe it's algae.

    I have owned and maintained this pool for 20 years and never had anything similar occur.
    I had the pool replastered in October 2008. Put in a new heater a couple years before that.
    City water. The rest of my pool specs are at the end of this post.
    Attached Images Attached Images
    32+ yr old (1982), 20x40, 17k; kidney, IG w/spa,
    gunite, Apollo VA38 DE filter, sta-rite lp gas heater,
    polaris cleaner w/auxiliary pump, chlorine

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    duraleigh's Avatar
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    Apr 2007
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    Sebring, Florida
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    Re: pool algae/stain help

    I'll take one issue....the black spots you mentioned. You tried vitamin C (to test for metal) with no effect. Did you put a tri-chlor tab on them? All stains are organic (test with a tri-chlor puck) or inorganic (test with Vitamin C). Those spots have to be one or the other and you should get SOME reaction when you try either a puck or the vitamin C. Have you tried a stainless Steel wire brush?

    Rather than try to fix all therse difficult issues at once, I suggest you focus on one until it's cured and then move to the next one.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

  3. Back To Top    #3

    Join Date
    Jun 2014
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    Glastonbury, Ct.
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    Re: pool algae/stain help

    hi Duraleigh,
    the nickel sized spots are the only spots I have not done extensive testing on. They are in the pool as opposed to the spa and so are more difficult to deal with. They are also the last spots to show up - first there was the smudge under the light, then the parenthesis shaped darker spots. I have been trying to deal with a subset of the issues - those that occur in the spa.

    I did this because I can control the environment of the spa much easier. I've used the puck and vit. C in the spa, jacks magic, concentrated chlorine and algaecide. I do have to admit that the spots in the pool caused me the greater concern, because they seem to be spreading throughout the pool, whereas the ')' marks seem to only be in the spa, and there's only 1 smaller smudge in the pool, but 2 larger ones in the spa.

    You seem to indicate that either/or vitamin C or tri-chlor puck should affect any stain/mark - one way or the other. Is this true and factual or is this simply something 'people say'? I ask because I've read a lot on many sites, and then done what I think is controlled testing (in my spa) and concluded that there's not a lot of hard facts available.

    I used the jack's magic because they indicate that their testing kit will determine factually whether a mark is a stain or not. (My presumption is that if the tests have no affect, it must be an algae.) They never outright state this, they just claim that their testing will determine what any stain is.

    With this in mind, then I'm leaning toward my spa stuff (smudges and ')' marks, being algae.

    The nickel spots I'll deal with next.
    32+ yr old (1982), 20x40, 17k; kidney, IG w/spa,
    gunite, Apollo VA38 DE filter, sta-rite lp gas heater,
    polaris cleaner w/auxiliary pump, chlorine

  4. Back To Top    #4

    Join Date
    Mar 2007
    Location
    San Rafael, CA USA
    Posts
    12,082

    Re: pool algae/stain help

    Quote Originally Posted by pnovak View Post
    You seem to indicate that either/or vitamin C or tri-chlor puck should affect any stain/mark - one way or the other. Is this true and factual or is this simply something 'people say'? I ask because I've read a lot on many sites, and then done what I think is controlled testing (in my spa) and concluded that there's not a lot of hard facts available.
    We deal with facts on this website. However, there's a third category which is for a copper stain which fades more with citric acid than with ascorbic acid. The Jack's Magic stain ID kit is more comprehensive for metal stain testing we normally recommend. If the stain were iron, it would readily fade with ascorbic acid. If it's copper, it may change with ascorbic acid, but not get removed.

    So all Jack's Magic tests were negative for metal stains? It could be that these are just deep copper stains so wouldn't show much reaction that quickly. Or if you haven't done the Trichlor puck test then the stains may be organic (e.g. leaves or black algae though they don't look like exactly like that). Trichlor will fade both organic stains and black algae. So if you haven't tried using Trichlor, I suggest you do so. If none of the Jack's Magic stain IDs used chlorine at low pH (which is what Trichlor does) then trying Trichlor will be different than what you have done.

    From what I can tell, the first test for Stain Solution #1 is for iron, cobalt, and spot etching. I suspect that test is ascorbic acid or other reducing agent that reduces iron effectively. The second test for Stain Solution #2 is for copper and scale so I suspect that this test is citric acid perhaps plus another stronger acid since that removes copper and calcium carbonate scale. The third test for O2 Shock and Stain Solution #2 is a non-chlorine shock treatment that makes deeper, tougher copper stains easier to remove so this is still a copper identification, but older copper stains. The fourth test for Stain Solution #2 followed by Stain Solution #1 is to remove iron scale (i.e. the combination of calcium carbonate scale with iron).

    So it looks to me like NONE of the Jack's Magic tests are for organic stains. Normally the acidity of Stain Solution #2 might have some affect on an organic stain, but only a mild one. The O2 Shock which is MPS non-chlorine shock usually isn't strong enough to oxidize organic stains. It is high chlorine concentrations that bleach out the colored chemicals in organic stains -- chlorophyll and to some degree tannins, most especially when a Trichlor puck is put over them. This is why we recommend testing with a Trichlor puck for organic stains. Jack's Magic focuses their business on metal staining and scale removal. They do not make products to remove organic staining because that's pretty much chlorine you can get for yourself.
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
    12 Fafco solar panels; Purex Triton PowerMax 250 natural gas heater (200,000 BTU/hr output); automatic electric pool safety cover; 4-wheel pressure-side "The Pool Cleaner"

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    Swampwoman's Avatar
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    Apr 2012
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    Grand Rapids, MI
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    Re: pool algae/stain help

    Greetings -- I can't offer much by way of insight for your stains, but just wanted to address this comment:
    I've had my water tested for metals and it shows a .6 level of copper and a similarly low number for phosphates. I do have something purported to remove the copper and will treat with that after next week, though I don't believe a low level of copper is complicit in these many problems.
    .6 ppm copper is NOT low -- copper will stain at .3 ppm. While maganese or silver typically produce blackish stains, copper can also turn blackish in some conditions. So your copper removal project may work

    In the event that it doesnt, If MA solution helped on one, you could aso try something like this spot remover brush designed for use with MA:
    Amazon.com : Purity Pool OS Out Spot Stain Remover : Swimming Pool Stain Removers : Patio, Lawn Garden
    In ground extended Grecian, 22,000 gal, Hayward 220t sand filter, vinyl liner, dolphin m4 supreme.
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