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Thread: 0 CYA - ok to use dichlor (shock) to increase CYA?

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    Join Date
    Jun 2011
    Location
    Central NJ
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    0 CYA - ok to use dichlor (shock) to increase CYA?

    Hi All,

    First up thanks to everyone, love this site, have learned so much, I switched last year from trichlor tabs and dichlor shock to BBB and just liquid bleach, had a great season!

    So I opened my pool this Sat, when I closed my pool last year CYA was about 35-40, I was surprised when it was 0 at opening (loads of leaves had gotten through the security cover somehow and must have caused the "swamp" effect and eaten all the CYA).

    Tested water (TF-100) before adding anything -

    Air temp - about 75F
    TA - about 90-100
    PH - about 7.2
    CYA - 0
    FC - 0

    I happened to have a bunch of unused di-chlor shock packs (aqua chem brand) from before i switched to using BBB, and knowing that it adds Chlorine and CYA I though i could use that to increase CYA. I added a pack and a half (one pack says 12,000 and i have an 18,000 gal pool) on Sat morning and then tested CYA on Sun night and it was still not registering, though FC was about 1 and CC was about 1, so I added another pack and a half and then tested Mon morning and finally the CYA test liquid was looking a bit cloudy but still not registering on the CYA tube (which has a min of 20, so I estimated it must be about 5 or so) FC was 1, CC was 4. Water had cleared up significantly and was looking much better.

    So I plan to keep adding the dichlor shock to bring the CYA up to about 30-35 or so and then stop and use BBB as usual. Any problems in using dichlor to increase CYA like this?

    thanks in advance!
    16.5 x 32.5 Vinyl lined IG (16,000 gal) oval shape, 3ft to 6ft deep, 1 HP pump (12-14 PSI) 4-6 hrs/day, Hayward Pro series High Rate Sand Filter S244S, Hayward CL220 Chlorine feeder (I have stopped trichlor tabs and switched to Bleach!), 1 bottom drain and 1 skimmer in, 2 returns.

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    JasonLion's Avatar
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    May 2007
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    Re: 0 CYA - ok to use dichlor (shock) to increase CYA?

    That is fine. Just keep an eye on the PH. Dichlor is very acidic, and your PH is already fairly low.
    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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    In the Industry


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    Re: 0 CYA - ok to use dichlor (shock) to increase CYA?

    Couple thoughts...
    CYA could take as long as 1 week to show up on your test.
    You can use Pool Calculator to figure out how much CYA each tab 'should' add
    Your CC continues to rise..makes me wonder how your water looks?
    Do you plan to shock the pool?

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    Join Date
    Jun 2011
    Location
    Central NJ
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    Re: 0 CYA - ok to use dichlor (shock) to increase CYA?

    Quote Originally Posted by JasonLion
    That is fine. Just keep an eye on the PH. Dichlor is very acidic, and your PH is already fairly low.
    Thanks, yes i'll keep an eye and raise as needed, also there's some aeration from the returns so it tends to bring up PH slighly....
    16.5 x 32.5 Vinyl lined IG (16,000 gal) oval shape, 3ft to 6ft deep, 1 HP pump (12-14 PSI) 4-6 hrs/day, Hayward Pro series High Rate Sand Filter S244S, Hayward CL220 Chlorine feeder (I have stopped trichlor tabs and switched to Bleach!), 1 bottom drain and 1 skimmer in, 2 returns.

  5. Back To Top    #5

    Join Date
    Jun 2011
    Location
    Central NJ
    Posts
    12

    Re: 0 CYA - ok to use dichlor (shock) to increase CYA?

    Quote Originally Posted by blakej
    Couple thoughts...
    CYA could take as long as 1 week to show up on your test.
    You can use Pool Calculator to figure out how much CYA each tab 'should' add
    Your CC continues to rise..makes me wonder how your water looks?
    Do you plan to shock the pool?
    they aren't tabs, they are granules actually in a pack, but thanks for the advice, i checked the calc and each pack will increase CYA by only 3.4 so it'll take a lot of dichlor, i think i'll go get some stabilizer and add it, will be faster, my local pool store seems to have some powdered form of stabilizer, will check it out.

    water was quite murky when opened, but it's much better now. yes i plan to shock with bleach but wanted to get CYA up to a reasonable level first....

    thanks!
    16.5 x 32.5 Vinyl lined IG (16,000 gal) oval shape, 3ft to 6ft deep, 1 HP pump (12-14 PSI) 4-6 hrs/day, Hayward Pro series High Rate Sand Filter S244S, Hayward CL220 Chlorine feeder (I have stopped trichlor tabs and switched to Bleach!), 1 bottom drain and 1 skimmer in, 2 returns.

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