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Thread: Shocking amount of chlorine needed?

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    Spiccolli's Avatar
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    Shocking amount of chlorine needed?

    First post!
    I have had this pool for 10 years, but am just now learning proper chemistry, so please bear with me

    so I guess I don't really get the fc, cya, shock relationship. According to the chart, my target fc is 6-7 based on my cya. shock level is listed at about 22. Currently, I have 1.5 fc.

    I need to raise my fc by 20.5? and I need to keep it there until overnight loss is < 1, cc is < .5, and water is clear. Is this correct?

    If so, that means I need to dump in 362 oz of 10% or 57 oz of cal-hypo 65 ?!?

    This seems like an awful lot of chlorine. If this is accurate, and I keep the level @22 until proper numbers are reached, how long is it going to take for all this chlorine to go back down to target level of 6-7? 13 days? is it safe to swim during this time?

    Thanks in advance for helping a newb!
    1992 15X30 14000 Gal IG plaster, Pentair 011018 - Intelliflo VS Pump with Timer, 350 lb Sta-rite hrpb30 sand (yeah, the 32-bolt clamshell)

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    JasonLion's Avatar
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    Re: Shocking amount of chlorine needed?

    You can swim any time FC is below shock level, the water is clear, and CC is 0.5 or lower.

    What is your CYA level? Assuming it is fairly high, then yes it takes a very high FC level to reach shock level. That is one of the main reasons we don't recommend having your CYA level that high.

    Do you have a specific reason you need to shock? You didn't mention one. Unless you have a specific reason to shock, you shouldn't shock.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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    Spiccolli's Avatar
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    Re: Shocking amount of chlorine needed?

    my last cya was 55, 2 days before that it was 40. These readings are from the pool store (I know now I need to do these readings myself as the pool store is not accurate - tf kit on the way).
    I have no idea how it could go up 15 ppm in 2 days as I have added nothing to increase it ( i used cal-hypo to up my fc after I performed a major water drain to drop cya - it was previously 150)

    As far as having a reason to shock, I have 1.5 fc and 5.0 tc. Doesn't that mean that I have 3.5 cc?
    Don't I have to shock to drop cc down below .5?

    by the way - i have FULL sun for 8-10 hours/day and temps here in AZ hit well above 100, sometimes in 115 range! - my last water temp reading was 88.

    Thanks so much for your help!
    1992 15X30 14000 Gal IG plaster, Pentair 011018 - Intelliflo VS Pump with Timer, 350 lb Sta-rite hrpb30 sand (yeah, the 32-bolt clamshell)

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    JasonLion's Avatar
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    Re: Shocking amount of chlorine needed?

    Your CYA level can't go up 15 in two days unless you added CYA. That is testing error at the pool store. That makes it somewhat speculative to guess what the CYA level really is. It could just as well be 40, or something else entirely.

    If your FC is 1.5 and TC is 5 then yes CC is 3.5 and you need to shock. But again there is some chance of testing error at the pool store.

    I suggest raising FC a bit above normal each evening, and waiting until your TF-100 shows up and starting over with more reliable test results. If you are really in a hurry, you could raise to shock level each evening, but I am not at all sure that is really required.
    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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    Spiccolli's Avatar
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    Re: Shocking amount of chlorine needed?

    Thanks Jason,
    Guess I'm just anxious to get everything right - we are now in full summer swim mode here and I want the cleanest pool on the block. The more I learn about pool chemistry, the more I want to get it in line so that it is easier/cheaper to take care of. It's also nice to swim knowing that the water is in proper balance - we won't get bloodshot eyes or stink like a bleach factory like after swimming in the public pool.
    1992 15X30 14000 Gal IG plaster, Pentair 011018 - Intelliflo VS Pump with Timer, 350 lb Sta-rite hrpb30 sand (yeah, the 32-bolt clamshell)

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    Re: Shocking amount of chlorine needed?

    I know how you feel - I'm in Las Vegas, and it gets Hades-hot here too! My water temp is only at about 82 (but with the solar heater running for the day, it hits 88-90, and OMG, it's so nice to swim in!).

    My plaster on my pool is in rougher shape than I'd like, but friends and guests are blown away by my water clarity (and I'm still not satisfied). If there's no wind and the surface is still, it can totally look like there's nothing in it.

    So keep at it! It's sooo worth it, especially when they ask what you're using, and you just hold up a bottle of Clorox and give them a blank look; the reaction is priceless!
    6000gal IG gunite // Hayward cartridge filter // rooftop solar heater // 32ppm borates
    Only two chemicals go in my pool! - bleach and muriatic acid!

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    Mod Squad jblizzle's Avatar
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    Re: Shocking amount of chlorine needed?

    Welcome from down South

    Hard to argue with anything Jason said.

    I will point out though that cal-hypo is adding CH to your pool ... and we here (in AZ) tend to have high CH in our tap water and it continues to go up due to lots of evaporation.

    So, I urge you to switch to liquid chlorine that does not add anything you do not need.
    Jason, TFP Moderator
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    Spiccolli's Avatar
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    Re: Shocking amount of chlorine needed?

    Quote Originally Posted by brainchasm
    when they ask what you're using, and you just hold up a bottle of Clorox and give them a blank look; the reaction is priceless!
    hilarious.

    Quote Originally Posted by jblizzle
    Welcome from down South

    I will point out though that cal-hypo is adding CH to your pool ... and we here (in AZ) tend to have high CH in our tap water and it continues to go up due to lots of evaporation.

    So, I urge you to switch to liquid chlorine that does not add anything you do not need.
    Thanks for the welcome! - glad to be here.

    I'm well aware of the hard water here, it has always been terrible on everything it comes into contact with until we put in a softener. The only way to plumb it involved softening the water that goes to the bib out back. This is the bib that has a line to the auto filler. So my problem now is not so much calcium anymore, but I gotta watch the salt. My tf kit is on the way, so i will be watching everything from now on.

    I'm just finishing up a bucket of granual that I got on sale a couple months ago. Once this is gone, I am 10% forever!!!! - special thanks to troublefreepool.com - i would have never known.

    I priced the 10% four packs at the local pool store vs. a 4.5 gallon clorox pricing at costco (i avoid walmart and sams like plague) and the 10% is a bit cheaper and i get to support my local business instead of the walchinamart.
    1992 15X30 14000 Gal IG plaster, Pentair 011018 - Intelliflo VS Pump with Timer, 350 lb Sta-rite hrpb30 sand (yeah, the 32-bolt clamshell)

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