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Thread: combined chlorine problem

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    combined chlorine problem

    I'm trying to get a handle on my pool before I go broke. Towards the end of last year I cleaned behind my lights and found what I now know was white water mold. There was quite a bit of it and I don't believe I got it all before we closed up for the season. This year I opened in mid-April to a pool full of white slimy toilet paper looking stuff all over. I've since been fighting this. The pool actually cleared up very nicely, but I've continued to have high combined chlorine. I started to shock yesterday around 1pm and have been adding shock every half hour to keep my FC above 15. It's been as high as 25. I even got up during the night to keep putting more in, but my CC hasn't budged. I've now added 48 bags of 66% Cal Hypo and I need to get more now, but I want to make sure I'm on the right track. Any help would be appreciated. One final note is that I had very high CYA at the end of last year and opened with little to no CYA. It was hard to tell based on the condition of the water, but it is now definitely 40.

    FC 15-25
    CC 2
    CYA 40
    PH 7.2
    TA 130
    CH 300
    18x36 vinyl pool
    chlorinator
    sand filter
    1.5 hp pump runs 24 hours per day

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    Mod Squad JVTrain's Avatar
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    Re: combined chlorine problem

    Welcome to TFP!

    The first red flag is you having high CYA last year and none this year. This typically means CYA to ammonia conversion which depending on how much residual ammonia is remaining when opening will have EXCESSIVE chlorine demand. Ammonia in the pool reacts with chlorine so quickly you can't even hope to hold any FC level for even 30 minutes. You have to just keep dosing with chlorine until all the ammonia is oxidized.


    Since you now have CYA, you're likely past that stage and are actually dealing with organics in the pool. CH is fairly irrelevant in vinyl lined pools, but the cal-hypo you're using is increasing your calcium level to the point where it may eventually cause scum or build up at the water line. If you still have some cal-hypo on hand, you can likely use it as your CH isn't that high yet. But, I would switch to bleach for adding chlorine. Nothing you don't want in bleach other than a little salt. As an aside... how did you have no CYA and now have 40 ppm?

    The other very important question is how are you testing? Test kit? Pool store? Check out our test kit comparision. Pool School - Test Kits Compared The TF-100 is the best kit money can buy and the K-2006 is a suitable alternative. Pool store testing is inconvenient and inaccurate. It also comes with a dreadful, uninformed sales pitch.

    Check out Pool School - ABCs of Pool Water Chemistry It's the foundation of everything we teach here at TFP.
    Joel - TFP Moderator - Minnesota - **Become a TFP Supporter!** Helpful Links: ABCs of Pool Water Chemistry - SLAM Procedure - Chlorine/CYA Chart
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    Mr Bruce's Avatar
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    Re: combined chlorine problem

    Hi michiganman, welcome! Thanks for filling out your signature and posting test results, good first post!

    Sounds like you have a good idea of the SLAM process but might be missing a couple of things. Read this a few times Pool School - SLAM - Shock Level And Maintain

    My thoughts:
    - Just use bleach/liquid chlorine for now. That Cal-Hypo is just going to drive up your CH.
    - Every 30 minutes is a bit excessive You can go an at least an hour between testing and adding. Much more than that is a waste of testing supplies IMO.
    - Your SLAM target is 16. Pool School - Chlorine / CYA Chart Don't go too high over that.
    - POP = Pool owner patience. You are less than 24 hours into a SLAM, it may take a couple days to a week.

    Again, read the SLAM article I posted a couple of times and let us know if anything is unclear, pun not intended
    32K gallon Plaster - CircuPool SJ-55 SWG - 1hp Hayward 2 speed Super Pump - Hayward S200 Sand Filter - TF100XL/K-1766
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    Re: combined chlorine problem

    Thanks for the reply. I started off using 3" pucks so I assume that's how it got to 40. It is possible that it wasn't quite 0 either as it was very difficult to tell with all the WWM in the water. I use the Taylor k-2006 for testing. I also just tested and estimate that I lost 10ppm of free chlorine from 3am to 8am this morning. That is down from 4.5ppm per hour when I first started this process. Should I be seeing my CC level go down yet? Also, if it is Amonia do I need to raise my shock level even higher than 15? Thanks!
    18x36 vinyl pool
    chlorinator
    sand filter
    1.5 hp pump runs 24 hours per day

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    Mod Squad tim5055's Avatar
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    Re: combined chlorine problem

    With obvious organics in the water I wouldn't even worry about the CC for now.

    I have to ask, are you following our SLAM guidelines? If so you would not get to 25 with your FC. We want you to be adding measured doses of chlorine (liquid preferably) which will "maintain" a level of 16. You really want to attain Shock Level And Maintain it there.

    There are three tests to pass a SLAM

    Pass Overnight Chlorine Loss Test
    CC less than .5
    Clear water, which includes no visible organics.

    If you see stuff in the water you know you don't pass that test, so there is no reason to even bother with the other two tests.

    A little over on the FC is OK, but in your example you overshot by 50%. That can be a recipe for bleaching a liner.
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    Re: combined chlorine problem

    Heya Michman- good to see another local guy here. (I lived in A2 from '85 until 2 years ago)

    We'll help you get a handle on costs. Avoiding pool $tore chems and potions is the foundation, but once you get clear water and start looking fwd to a nice swimming season, people like me will start pressuring you to ditch your single-speed pump (assuming it is) in favor of a 2 or variable speed motor instead. I did exactly that a few months ago. I wish it had been the first upgrade I did.

    We can also save you on some reagents and hassle right now in your testing routine during your SLAM: If you stop using Cal-hypo you won't have to closely monitor CH. Whenever your FC is over 10, the pH test will read falsely high, so you can hold off on that too. CC is essentially a given at this stage. CC results are most useful when the time comes when you need to determine if your SLAM is complete. (at which point your water will be clear)
    12,000 gal Diamond Brite indoor​ pool. Pentair Triton TR-60 Sand Filter +added DE, Lochinvar Energyrite ERN-200 gas heater, Pentair Multi-valve, Pentair SuperFlo VS pump, TF-100 kit, Pool Math App - iOS

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    Re: combined chlorine problem

    Thanks for everyone's help! I have read the SLAM process. The reason I went a little high in the beginning was twofold. 1.) I thought I had read where it would take 10x the CC if amonia was in the water. 2.) The FC was dropping at 4.5ppm per hour in the beginning so I wanted to make sure I didn't dip below 16ppm. Is it ok if it dips below that? Otherwise I'm going to need to add liquid chlorine every hour since I'm still losing 2ppm per hour. Thanks!
    18x36 vinyl pool
    chlorinator
    sand filter
    1.5 hp pump runs 24 hours per day

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    Re: combined chlorine problem

    Update: I've switched to liquid chlorine 10% from Walmart ($3/gallon). At 1pm I measured 16ppm FC. I added 1 gallon which should have taken FC to approximately 20ppm. At 2:30pm it measured 14ppm. It looks like I'm still losing 4ppm on average. Is this normal 24 hours into a SLAM?

    Also, the pool is noticeably clearer today because I can see the floor of the shallow end.
    18x36 vinyl pool
    chlorinator
    sand filter
    1.5 hp pump runs 24 hours per day

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    Re: combined chlorine problem

    The amount of loss you are having could or could not be normal. At SLAM level you will lose chlorine a lot faster than when you are within normal range. Also depends on the amount of sun or could be that your bleach has lost some of its strength.

    The only time chlorine loss is an indicator during the SLAM is during OCLT. Make sure your last dose of chlorine comes after the sun goes down. Then test FC level an hour later to see where you're at. Go to bed and test again right before sun comes up. If your FC loss is more than 1, then you need to keep on SLAMing
    16,000 gallon in-ground pebble tec pool. Hayward SP3400VSP Eco-Star Pump, Pentair Triton 2 TR-100 sand filter, A&A 5-port in-floor pool cleaner, Pentair Intellibrite 5g color changing pool light, Polaris 965iQ Robotic Pool Cleaner, OG Pool Math Subscriber and most importantly a Taylor K-2006C test kit.
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    | SLAM | Chlorine / CYA Chart |

  10. Back To Top    #10

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    Re: combined chlorine problem

    Thanks. I appreciate the explanation. When you're spending so much money it's always good to hear that you're on the right track.
    18x36 vinyl pool
    chlorinator
    sand filter
    1.5 hp pump runs 24 hours per day

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    Re: combined chlorine problem

    How does the water look? Can you post a pic?
    12,000 gal Diamond Brite indoor​ pool. Pentair Triton TR-60 Sand Filter +added DE, Lochinvar Energyrite ERN-200 gas heater, Pentair Multi-valve, Pentair SuperFlo VS pump, TF-100 kit, Pool Math App - iOS

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    Re: combined chlorine problem

    Rollercoastr, it's getting a little better each day. This is a pic from this morning showing what I believe is algae laying on the bottom in 4 ft of water. I can see my deep end drains again today. I'm maintaining shock level continuously and I'm able to go a little longer between additions of chlorine. I have a filter cleaning chemical for my sand filter. I'm wondering if I should use that now or wait until this process is complete? I am seeing a little sand in the pool when I sweep so I think I have a broken lateral.
    18x36 vinyl pool
    chlorinator
    sand filter
    1.5 hp pump runs 24 hours per day

  13. Back To Top    #13

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    Re: combined chlorine problem

    Good to hear! I can't see a pic tho?

    Before adding a chemical to the filter, you might want to try a "deep clean" - particularly since you suspect internal damage anyway. Here's a great thread about that process: Deep Cleaning a Sand Filter

    (I'm a fan of DE in a sand filter. Cheap, easy and effective, but I wouldn't do it until your filter is proven to be intact)
    12,000 gal Diamond Brite indoor​ pool. Pentair Triton TR-60 Sand Filter +added DE, Lochinvar Energyrite ERN-200 gas heater, Pentair Multi-valve, Pentair SuperFlo VS pump, TF-100 kit, Pool Math App - iOS

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    Re: combined chlorine problem

    Sorry, I can't seem to attach the picture. It's telling me that I do not have permission
    18x36 vinyl pool
    chlorinator
    sand filter
    1.5 hp pump runs 24 hours per day

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    Re: combined chlorine problem

    Is it a really large file? It may exceed the size limitation. You could try to reduce the size of the file before posting, or upload it to a hosting site and paste the a link to it instead. Flickr, Photobucket, Google Drive, Microsoft Onedrive are a few of the options.
    12,000 gal Diamond Brite indoor​ pool. Pentair Triton TR-60 Sand Filter +added DE, Lochinvar Energyrite ERN-200 gas heater, Pentair Multi-valve, Pentair SuperFlo VS pump, TF-100 kit, Pool Math App - iOS

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