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Thread: Oops, added way too much chlorine

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    Join Date
    Oct 2010
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    Houston, TX
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    Oops, added way too much chlorine

    So I was losing ~4ppm chlorine per day on my 4500 gallon spa. Did an overnight FC loss test and it was 1.5ppm, so I decided to shock the spa. CYA was 40 and FC was 4 before shocking, and after 182oz of chlorine in the morning and a day in the hot Texas sun, FC was 14.

    Shock level goal was 16, and I wanted a bit extra for some wiggle room, so i added 64 oz of chlorine. After a few hours, the FC is >30 (measured it three times).

    So, I read here that chlorine can damage equipment. Should I do a partial drain, or just let it be as there may be still some algae and along with the texas sun may bring it down a decent amount? Thanks
    15k gunite pool. Intelliflo VF. Autopilot SWG.
    2k separate spa with waterfall (ie: pain in the rear maintaining a separate body of water). 2HP Hayward Tristar pump.

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    Cupertino, CA
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    Re: Oops, added way too much chlorine

    Wow, monster spa, awesome!

    The Pool Calculator suggests that the 182oz was worth 20ppm and 64oz was worth about 7ppm, assuming 6% bleach. Was it 6%, or something stronger? because that all adds up to 31ppm, and after a day in the sun it should've dropped some. March sun isn't exactly the strongest, but still.

    At those levels, you don't want to skimp on the R-0870 powder when you run your test. Be sure to wait a second or two between drops of R-0871, going too fast can lead to inconsistent results.

    I don't know anything specific about super high FC causing equipment issues, usually it's pH or scaling situations where you get in trouble, and those basically aren't affected by chlorine. (Note your FC does interfere with the pH test, so don't bother testing pH until FC is down in the 10-ish range.)

    If you're worried about excess FC, probably the stuff easiest to lay your hands on is hydrogen peroxide. I make it about 7oz of 35% peroxide, or 92oz 3% peroxide, to lower FC by 10ppm in 4500 gallons. (Based on this topic, chem geek's reply near the end.)
    --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
    AG spa 325 gal, probably Sundance of some kind
    Water testing instructions on one page

  3. Back To Top    #3

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    Re: Oops, added way too much chlorine

    With a CYA of 40, your equipment will be fine. You just wouldn't want the chlorine that high over an extended period of time or as a target, but it'll drop over the next days. Even if you didn't have unusual chlorine demand, it would still drop around 25% per day with a hot spa so will get down pretty quickly.
    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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    Oct 2010
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    Houston, TX
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    Re: Oops, added way too much chlorine

    Quote Originally Posted by PaulR
    The Pool Calculator suggests that the 182oz was worth 20ppm and 64oz was worth about 7ppm, assuming 6% bleach. Was it 6%, or something stronger? because that all adds up to 31ppm, and after a day in the sun it should've dropped some. March sun isn't exactly the strongest, but still.

    At those levels, you don't want to skimp on the R-0870 powder when you run your test. Be sure to wait a second or two between drops of R-0871, going too fast can lead to inconsistent results.
    Yeah, just started doing BBB back in around January, and it's only recently that the water has been getting warm (other than when I used the spa). I still haven't figured out how much chlorine to add each time as it has been pretty inconsistent... perhaps because I had low level algae for a while...


    Quote Originally Posted by chem geek
    With a CYA of 40, your equipment will be fine. You just wouldn't want the chlorine that high over an extended period of time or as a target, but it'll drop over the next days. Even if you didn't have unusual chlorine demand, it would still drop around 25% per day with a hot spa so will get down pretty quickly.
    That's a relief. Seemed like a waste to lower the chlorine just to add more a few days later.

    You guys wouldn't happen to know if I would have to brush the waterfall as well if I had low-level algae? And would I have to run the waterfall for a long period of time as well as the pump?
    15k gunite pool. Intelliflo VF. Autopilot SWG.
    2k separate spa with waterfall (ie: pain in the rear maintaining a separate body of water). 2HP Hayward Tristar pump.

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    JasonLion's Avatar
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    Re: Oops, added way too much chlorine

    It is certainly a good idea to brush the waterfall, though not usually essential. You do need to run the waterfall for at least a while when the FC level is high to make sure any algae there is killed.
    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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