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Thread: Water turning green after liquid chorine added

  1. #1
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    Water turning green after liquid chorine added

    Hi. New to the forum. Checked back a few pages and don't see my problem addressed. We have a 24ft, 48" deep, round AG pool. It has a vinyl liner and a sand filter. The pool, liner & filter are approximately 13 years old. We've been in the house 6 years so we replaced our filter sand last year. Our water source is well water (recently tested negative for copper with a trace amount of iron). I'm in southern Ontario and our pool season runs from late May to early September.

    Up until last year we'd never had any problems with water quality or staining. Starting last year we had a minor amount of yellowy-brown staining on the walls of the pool. I put it down to my husband neglecting to clean the walls before he filled the pool in the spring and as it was very minor we lived with it. We're in a rural area and this past winter we had a major windstorm that blew soil from the surrounding fields all over the place - some of this soil would have got into the pool when the winter cover was partially blown off due to the high winds. This year my husband again didn't clean the walls before filling up the pool. After filling up the pool in the spring and clearing the water, we noticed we had staining on the floor of the pool together with the walls. This gave the pool a decidedly green appearance. When tested, the water analysis figures were always within acceptable parameters. I started doing research on the internet and read about the vitamin C test. Tried it and watched the stains disappear before my eyes. Bought Stain Free and Metal Free and used them according to instructions. The pool turned beautifully blue and totally crystal clear within 12 hours, but when I woke up the next morning, the water had a white, cloudy appearance. Took a sample to our pool store and all levels tested fine with the exception of chlorine which was nil (as per the instructions on the bottle). Pool store told us to add chlorine which we did only to see the pool turn a cloudy green colour. Over the next few days, as the chlorine levels dropped, the water returned to a blue colour, but it was somewhat cloudy. Phoned Natural Chemistry and they said to add DE to the filter, put in another bottle of Metal Free, run filter continuously for 24 hrs and then backwash and add chlorine slowly. Put the Metal Free in and once again and water turned blue, but still a bit cloudy. After 24 hours I backwashed and then I added a litre of liquid chlorine and the pool water has turned green again!. I'm getting quite frustrated. Everything that I'm reading points to this being a metal problem, but both pool and well water are testing negative. One site that I was on where someone had the same problem said to add HTH Pool Stabilizer to clear the water.

    Does anybody have any idea what I can do to get clear water again?

  2. #2
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    Re: Water turning green after liquid chorine added

    Can you post the test results?

    We need pH, total alkilinity (TA) calcium hardness, stabilizer levels (CYA), free chlorine, and combined chlorine.
    What you added in the Metal Out was an ascorbic acid (vitamin C) product that lifted the iron off the surface of the pool. The metal is still there, however. It must be bound by a sequesterant to eliminate the green color. I think Metal Free is a sequesterant, somebody can correct me on that, but my guess its an EDTA based chelator since its put out by Natural Chemistry. What we recommend is a phosphonic acid based sequesterant. That is what the HTH Metal control is (not HTH stabilizer).
    I cant readily address the cloudiness at this point until you post some test numbers.
    The constant chlorine, green, sequesterant, chlorine, green loop is a tough one sometimes.
    14,000 gallon IG, Vinyl. Hayward 3/4 hp superpump, Penatair IC40 SWCG, Pentair automation, Hayward sand filter, Aqua Comfort heat pump, Hayward 400k Lo-Nox LP heater.

  3. #3
    Administrator JasonLion's Avatar
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    Re: Water turning green after liquid chorine added

    From your description, you have iron in the water. I am not at all fond of Metal Free, it is not one of the more effective sequestrants. Sequestrants based on HEDP, phosphonic acid, or phosphonic acid derivatives are the most effective.

    When doing an ascorbic acid treatment, which is what Stain Free is, it is very common for the water to get cloudy for a day or two when you add sequestrant. It is also possible to get algae while the FC level is zero during the treatment. It is always a little tricky to tell if you are getting algae or not, since the appearance is nearly identical.

    Anyway, if the water turns a clear transparent green when you add chlorine that is from the iron in the water, and indicates that you are not using enough sequestrant. From your description, it is not completely clear if that is what happened, but it seems likely. The solution is to add more sequestrant.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    TFP Admin. Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

  4. #4
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    Re: Water turning green after liquid chorine added

    Thanks for replying so quickly.

    Just had the water tested. I didn't ask them for any advice because we've found that all they seem to be interested in is selling expensive chemicals. In all the years we've been here we've only used liquid chlorine, granular chlorine and, very rarely, a bit of algaecide as a preventative.

    The results were:

    Water Colour - none
    Water Clarity - clear
    Free Chlorine - 1.5
    Total Chlorine - 1.9
    Combined Chlorine - 0.4
    pH - 7.6
    Hardness - 270
    Alkalinity - 110
    Cyanuric Acid - 10

    In reading both of your posts, I'm getting the feeling that there is probably still metal in the water. I still have 1/2 a bottle of Metal Free. Should I try using that before I buy another sequestrant? Do I have to get the chlorine down below 1.0 before I put it in? I'm confused as to why there is so much metal in my water. We only top-up the pool using our well water and we just had that tested because we need another water softener and the results came back with no copper and such a minute trace of iron that the salesperson said that it wasn't a concern. The pool store also tested for both and came back with none. Is there any other way that metals can get into the pool? We don't have a heater.

    As far as algae goes, it has never been an issue for us. Would the water not look somewhat green all the time if it was algae? Thing is, when the chlorine level is nil the water is blue - it's only after the chlorine is added that things go green.

    Pool store has recommended that we shock the pool tomorrow at sundown, but needless to say I'm very hesitant to do it.

    Thanks in advance for your help.

  5. #5
    Administrator JasonLion's Avatar
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    Re: Water turning green after liquid chorine added

    If the water turns green when you add chlorine and then turns blue again as the chlorine level falls there are certainly metals in the water, either iron or copper or both. I'm guessing iron, but it could be copper. Adding enough sequestrant will solve the problem.

    Having the pool test free of metals, when there are obviously metals in the water, happens often enough, even though it shouldn't. That is just testing error, it happens.

    You can add sequestrant even when there is chlorine in the water. You want to lower the FC level as much as possible before using ascorbic acid/stain free, but that isn't needed when adding sequestrant.

    Metals are often in well water. They can also be etched out of metals parts in the plumbing if the PH is very low for a while. There is also copper in some kinds of algaecide, and various "mineral" treatments (such as Nature2). Many HTH chemicals also contain some copper.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    TFP Admin. Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

  6. #6
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    Re: Water turning green after liquid chorine added

    Morning & thanks for the info. I totally agree about the metals in the water, but still can't figure out why neither the pool store or water store tested positive for copper or iron. In talking further to the guy at the water store, he suggested that it was possible that due to possible fluctuations in our water table our water may have been coming from different aquifers at different times. If that's the case, fingers crossed that the metals source aquifer doesn't reappear.

    I decided that I had nothing to lose yesterday as far as the stabilizer suggestion went so I put 12 oz. of it in a sock yesterday afternoon and believe it or not I woke up to a clear, blue pool this morning! I'm amazed. It will be interesting to see what I end up with tomorrow morning after I dose the pool with chlorine tonight.

  7. #7
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    Re: Water turning green after liquid chorine added

    Quote Originally Posted by midge
    In talking further to the guy at the water store, he suggested that it was possible that due to possible fluctuations in our water table our water may have been coming from different aquifers at different times. If that's the case, fingers crossed that the metals source aquifer doesn't reappear.
    He's just grasping at straws, really. Several here, including myself, have iron in the pool water that tints the water green but cant be detected by testing. We are not sure why, so anything would be speculation. My best guess is that metal that tints the water may do so at levels below the detection of the test. But again, thats a guess.

    Quote Originally Posted by midge
    I decided that I had nothing to lose yesterday as far as the stabilizer suggestion went so I put 12 oz. of it in a sock yesterday afternoon and believe it or not I woke up to a clear, blue pool this morning!
    I'm not sure what you mean here. You added stabilizer (cyanuric acid) and the pool was clear the next morning? CYA only stabilizes chlorine; it does nothing for metal treatment. The clear pool is great, but the stabilizer didnt have anything to do with it.
    14,000 gallon IG, Vinyl. Hayward 3/4 hp superpump, Penatair IC40 SWCG, Pentair automation, Hayward sand filter, Aqua Comfort heat pump, Hayward 400k Lo-Nox LP heater.

  8. #8
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    Re: Water turning green after liquid chorine added

    Stabilizer and sequestrant are 2 totally different things. Though if your CYA is at 10 then you probably need some more stabilizer. Stabilizer doesn't solve the metal issue.
    Mona SE MN
    24' round 48" high AG
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  9. #9
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    Re: Water turning green after liquid chorine added

    Quote Originally Posted by bk406

    Quote Originally Posted by midge
    I decided that I had nothing to lose yesterday as far as the stabilizer suggestion went so I put 12 oz. of it in a sock yesterday afternoon and believe it or not I woke up to a clear, blue pool this morning!
    I'm not sure what you mean here. You added stabilizer (cyanuric acid) and the pool was clear the next morning? CYA only stabilizes chlorine; it does nothing for metal treatment. The clear pool is great, but the stabilizer didnt have anything to do with it.

    Sorry, didn't explain myself very well. In doing research about chlorine turning water green, I came upon the answer I've pasted below at wiki.answers.com (I know, I know - not a reliable source, but the only answer I found that had a simple suggestion that I knew wouldn't harm my pool's levels). There was also a response to this answer by someone who had tried it and it had worked for them as well. I used a lesser amount of stabilizer just in case it made things worse.

    -----"Answer: My pool also turns green within 20 mins - solid dark green, darker than the grass, but still clear - after adding chlorine pool tablets. I have well water and have filled it from that each time this has occurred. I am not sure of the cause, but I figure copper, sulfur or iron, or all of them are present.
    The cure is simple. Once the chlorine is testing correctly, I go to the Walmart and get HTH Stabilizer. Add 2 full caps (the cap is big like 16 oucnes) for a 24 foot round by 52 inch deep pool and let the filter run for 24 hours straight. It will be crystal Clear by then. You will see it start to clear withing the hour. Once clear, backwash your filter for about 3-5 minutes, then run it on rinse a minute, and then return to filter. All the green will be gone and you are set for the season.
    If it is a clear green then it is copper. go to the grocery store and buy ALUM, found in the spice isle a few bottles of this will safely remove the copper and is safe to swim in.
    it is the same alum used to make pickles."-----

    I figured I didn't have anything to lose and I have to say this is the first time the pool hasn't been cloudy since I did the Stain Free treatment a week ago. It will be interesting to see what happens after I shock the pool tonight.

    Does anybody have any comments on the "alum" suggestion?

  10. #10
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    Re: Water turning green after liquid chorine added

    Stabilizer/CYA lowers PH a little. Usually by lowering PH this can change the chemical reaction color you see between metals and chlorine somewhat. So that may explain a bit why they noticed a difference, but IMHO more likely it was just coincidence cuz the high chlorine level is wearing off, and/or the metal sequesterant is working.

    The ONLY thing that removes copper is water replacement. Do not use Alum.

    If you want to maintain things with the HTH Metal Control that would be a safe choice.

    Why are you planning to shock the pool? That's not clear to me.
    Helpful links: Pool School; CYA/Chlorine Chart
    24' round AG pool, 52" high, Raypak heater; Waterway 2 spd Pump;
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  11. #11
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    Re: Water turning green after liquid chorine added

    Quote Originally Posted by frustratedpoolmom
    Why are you planning to shock the pool? That's not clear to me.
    Because the pool store said to . Just kidding. Had a bunch of kids in the pool last night, the temps today are quite high and thunderstorms are supposed to start rolling in overnight. I used an Aquarius testing kit this morning and the chlorine showed between 0.5 & 1.0. Wish I could get to the pool store, but it's a 20 mile drive and I don't have time today. We've never needed a good quality testing kit before because we've never had problems, but the next time I'm at the pool store I'll have a look.

    Thanks for the info on the alum. What is the difference between the Metal Free and the HTH?

  12. #12
    Administrator JasonLion's Avatar
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    Re: Water turning green after liquid chorine added

    The HTH sequestrant uses one of the chemicals we recommend, one that is much more effective than the stuff they use in Metal Free.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    TFP Admin. Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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