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Thread: Spa free chlorine suddenly rising very high

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    Spa free chlorine suddenly rising very high

    Yesterday we tested our spa FC to be 25! Strange thing is we had not added any chlorine to the spa to cause this rise. Today we retested the water after leaving the lid open all night and found the FC to be above 30 by then I had just stopped adding drops.No chlorine had been added? I just dont know what is going on to cause this. Any ideas? Im thinking of draining and starting over but sure would like to understand what is going on here.
    27 foot round above ground

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    cowboycasey's Avatar
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    Re: Spa free chlorine suddenly rising very high

    there is no way chlorine is rising on its own, something is in it adding to it... do you have a frog system or something like it? are there pucks in it your not seeing?
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    Re: Spa free chlorine suddenly rising very high

    I was reluctant to even post this because I know that what you say is true. I just don't get it. I want to test it again and find out I just did something brain dead like I sometimes can do. I do not have any sources of chlorine that feed the spa. I simply add some after each use as needed.
    27 foot round above ground

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    cowboycasey's Avatar
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    Re: Spa free chlorine suddenly rising very high

    hmmm, are you using MPS or something non chlorine, that can have an affect on testing.. I am just not sure.. I use bromine and MPS about once a week..

    I am going to a SWG for the spa this winter so no more bromine and MPS

    Hopefully someone will have some more insight for you...
    Pool: Intex 16x32 15000 gal, 2 speed 340042, Pentair CC320 Filter, CircuPool SJ45 Salt System, Intermatic PE653RC; Hot Tub: 650 Gal SWG Megachlor
    links: pool school * Recommended-Levels * SLAM * CYA chart * Test kits * How To Post Pictures * Poolmath * OCLT ** Support your website if we helped you :) **

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    Re: Spa free chlorine suddenly rising very high

    Thanks for your reply. I appreciate your taking the time to ponder this ridiculousness of mine. I probably double dosed the spa not realizing it. Maybe the wife and myself both dosed it and just overdosed it. Im going to drain and clean it and hopefully it will be fine after that.
    27 foot round above ground

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    Re: Spa free chlorine suddenly rising very high

    Why not just leave it open and let it naturally come down?
    17.4k gallon IG pool with attached spa (spa itself is 730gal), Super Blue Diamondbrite plaster, Circupool SI-45+ SWG, BH/Hayward Cartridge Filter, 2hp 2speed Hayward Super II pump, , Jandy Valves, Waterway Skimmers, Rheem 400k Heater, Polaris 360 cleaner, built 2000+-, replastered June 2015, TF-100 kit---Here's my pool test reading history

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    Re: Spa free chlorine suddenly rising very high

    Or you can use hydrogen peroxide to lower it faster. You use the same amount of 3% hydrogen peroxide as the volume of 6% bleach in terms of FC -- that is, figure out the FC you want to drop, look up how much 6% bleach that would be (pretending you wanted to raise the FC by that amount), and then add that volume of 3% hydrogen peroxide to the spa to lower the FC.
    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
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    Re: Spa free chlorine suddenly rising very high

    Quote Originally Posted by chem geek View Post
    Or you can use hydrogen peroxide to lower it faster. You use the same amount of 3% hydrogen peroxide as the volume of 6% bleach in terms of FC -- that is, figure out the FC you want to drop, look up how much 6% bleach that would be (pretending you wanted to raise the FC by that amount), and then add that volume of 3% hydrogen peroxide to the spa to lower the FC.
    Gonna have to tuck that one away for later...cool!
    17.4k gallon IG pool with attached spa (spa itself is 730gal), Super Blue Diamondbrite plaster, Circupool SI-45+ SWG, BH/Hayward Cartridge Filter, 2hp 2speed Hayward Super II pump, , Jandy Valves, Waterway Skimmers, Rheem 400k Heater, Polaris 360 cleaner, built 2000+-, replastered June 2015, TF-100 kit---Here's my pool test reading history

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    Re: Spa free chlorine suddenly rising very high

    Some good info there chem geek. Thanks. I'm finding that the FC is slowly falling. So I must have done something stoopid. I am thinking about just draining the tub at this point and doing the water change that is due. Is it necessary to do the pipe cleaning thing every time you do this or is that just overkill?
    27 foot round above ground

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    Re: Spa free chlorine suddenly rising very high

    You don't have to do the Ahh-Some every time, especially if the water change is soon after the previous one, but for normal water changes it's not a bad idea to use it every time. You can see what comes out each time and decide based on that. Some spas get more material accumulated more quickly than others. Of course, if a spa wasn't consistently maintained, then the Ahh-Some should be used to remove any biofilms that may have formed.
    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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    Re: Spa free chlorine suddenly rising very high

    Thanks Richard. We have consistently changed our water every 3 months. We have always used some sort of biofilm treatment in doing so. We in fact did two disinfection processes in a row the first time we put the tub back in operation after it had sat for some unknown period of time. But I have noticed that we have been getting nothing out of the pipes when do the disinfection process. It is only the wife and myself using the tub and that is usually once a day for 30 to 45 min. and we maintain the FC at about 6-7 so it seems to stay very clean. So I think that every other fill may be sufficient. Thanks for your reply.
    27 foot round above ground

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    Re: Spa free chlorine suddenly rising very high

    So that sounds like 1 to 1.5 person-hours per day so if you were using the Dichlor-then-bleach method then if your spa is 350 gallons I'd expect you to be able to go (2/9) x (350) / (1 to 1.5) = 52 to 78 days between water changes so your changing every 3 months sounds about right unless I've got your spa volume way off.
    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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