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Thread: Chlorine / CYA Chart Question

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    Chlorine / CYA Chart Question

    New pool owner; had a basic question. I have a SWG system in my pool. I had to add 14000 gallons to my pool because it leaked out. Got the CYA up to level; added salt and got up all the other readings near or into the right range.

    However, yesterday I had a reading of 0 FC. I have put in Liquid Chlorine and started my SWG and set it to 50% output. But why should I go for a shock FC of 24 with a SWG system and a CYA of 60? If the water is clear and there are no problems why wouldn't I raise the FC to 6 or 7, why go so high as 24?

    Thanks.
    24000 gallon Gunnite Pool
    WhisperFlo 1.5 hp Pump
    AquaConfort SWG System
    Solar Heating System

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    Mod Squad Bama Rambler's Avatar
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    Re: Chlorine / CYA Chart Question

    If the water is clear and there is truely no other problems, you don't need to shock. Just bring your FC up to the target level and keep it there.

    Why did you think you needed to bring the FC to shock level?

    My question would be, why did your FC suddenly go to zero? Did your SWCG shut off for some reason or could it just not keep up?
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/¼hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
    Pool School ----- Pool Math ----- TF-Test Kit

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    Re: Chlorine / CYA Chart Question

    The water is a little cloudy; that's all. I didn't turn on the SWG system until yesterday; so it hasn't been running and I have not put in a lot of Chlorine at this point. I was going to add enough chlorine to at least bring it to the 4-5 level and then watch it just with the SWG running.
    24000 gallon Gunnite Pool
    WhisperFlo 1.5 hp Pump
    AquaConfort SWG System
    Solar Heating System

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    Mod Squad Bama Rambler's Avatar
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    Re: Chlorine / CYA Chart Question

    When you say "not a lot of chlorine" how much is that?

    That explains why your FC was zero. Since your pool is cloudy and your FC was at zero there's a good possibility that you'll have to shock.
    How did you refill your pool? (Well, municipal water, trucked in, etc)
    Do you have your own test kit and if so which one?
    You need to be able to perform a overnight chlorine drop test to tell if you need to shock.
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/¼hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
    Pool School ----- Pool Math ----- TF-Test Kit

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    Re: Chlorine / CYA Chart Question

    I added only 1 gallon of chlorine (12%), but I did that when there was little CYA in the pool (didn't know better, discovered this site later). I then added 2 gallons of liquid CYA which did not bring up the pool to the right level. Then I added 20 oz dichlor on Sunday, which from my understanding adds 1 part chlorine and 1 part CYA (about). I wanted to bring the chlorine level to about 6 oz. Took a measurement yesterday; and the chlorine level is at about 0.5 or so. Kind of hard to tell from the test kit (I have Leslie's DPD Complete Kit. I also tested with last years OTO kit I had and it gave me a reading of of 5 ppm. I didn't trust it since it was from last year and store testing confirmed very low levels). I also turned on my SWG generator and cranked it up to 50%; not knowing how much FC that generates since the manual doesn't tell me.

    So my thought was since the pool is only a little cloudy (I can see the drains in 7 feet water, but they are not clear) and there is no algae I only need to bring it up to 5-6 FC level. But does algae only exist when there is green stuff present? Does it exist and you don't see it and shocking is required? What's an overnight chlorine drop test; I didn't run across that yet in the forums; other than one or two references to it.

    Thanks for all the info.
    24000 gallon Gunnite Pool
    WhisperFlo 1.5 hp Pump
    AquaConfort SWG System
    Solar Heating System

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    Mod Squad Bama Rambler's Avatar
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    Re: Chlorine / CYA Chart Question

    Algae can exist even though you can't see it. A little cloudiness may be all you see or nothing at all. The fact that your using a lot of FC points to the fact that something is consuming it.

    The FAS-DPD is a chlorine test that can measure up to 50ppm of Fc and CC. It's required to do the overnight chlorine drop test and for proper shocking and especially to know when your finished. You can buy it as a stand alone kit from tftestkits.net
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/¼hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
    Pool School ----- Pool Math ----- TF-Test Kit

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    JasonLion's Avatar
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    Re: Chlorine / CYA Chart Question

    Here are instructions for performing the overnight FC loss test.
    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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