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Thread: Reclaiming the pool from algae

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    Reclaiming the pool from algae

    I posted part of my story in another thread but I am confused about getting rid of my algae and adding CYA. I went to the pool store yesterday and got these readings from testing:
    FC: 0
    pH: 8+
    TA: 60
    Ca Hardness: 240
    CYA: 0

    The filter was backwashed a bunch of times but has not been recharged since November. I know I need to raise my CYA but do I have to wait a week until I can start with bleach? Or can I start the process while the CYA is hanging in it's little sock. Also according to the Pool Calculator I will need 12lbs of CYA to get up to a good level, can I stick a sock in both skimmers and one in front of a return? Or should i add the CYA slowly, a sock at a time?
    Another question...if I have to wait a week until the CYA is up, can I run my system on circulate, bypassing the filter?
    40K IG Plaster w/ attached IG Spa
    1.5 HP Challenger Self Priming Pump
    0.5 HP Booster pump running a Polaris 360 rover
    60sq.ft DE Filter w/ Multiport Valve
    Fort Worth, Texas

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    JasonLion's Avatar
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    Re: Reclaiming the pool from algae

    The first two things to do are to get the PH down to around 7.2 and to raise CYA up to around 30. You can work on both of those at the same time. Go ahead and use a couple of socks if you need to. Getting the PH right will probably take a couple of tries. Don't trust the calculated value for how much acid to add, large PH changes are often off. So add about half as much as it recommends, give it an hour to mix in with the pump running, and then test the PH and TA again and proceed from there. By the time you get the PH down you will probably need to raise the TA level as well. You want TA around 60 to 80 for now.

    Once the PH is right, TA is at least close, and the CYA has been started, then start adding chlorine (using a shock level based on the assumption that CYA goes directly to 30 right away, even though it doesn't really).
    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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    Re: Reclaiming the pool from algae

    Hey,

    Welcome to the forum I've read your other thread, too.

    This stuff is complex but only at first. you will soon have a good grasp.

    I suggest you start in Pool School by reading the basic articles there. It will answer a lot of your questions.

    Before you start on the chlorine/CYA issue, bring that pH down into the mid 7's you could easily be higher than 8.0 and that's not good.

    So, once the pH is fixed, remember that chlorine is consumed by organics (including algae) present in your pool. The other thing that consumes chlorine is UV from the sun, so we use sort of an "umbrella" to PARTIALLY slow down that consumption of chlorine by the sun.

    So, when you are clearing algae, it is a good idea to have SOME CYA in the pool but not so much as to completely :shade" the chlorine because it becomes less effective.

    Again, all explained better than I can in Pool School.

    As sort of a guide, you would be fine to put in about 30ppm or so CYA and bring your FC up to around 12ppm to attain shock level and start to kill the algae.

    If you have calculated the dosage correctly (it sounds like you have) then I think it's safe to assume you have the CYA in there and begin shocking shortly after first adding the CYA.

    EDIT: Jason beat me to it so I am simply echoing what he said
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Re: Reclaiming the pool from algae

    Jason or Dave

    Would there be a problem with using granular tri chlor for a couple of days to maintain the pool to shock level?
    The tri chlor would lower the PH quickly and within a couple of days raise the CYA? After that then switch to bleach.
    Would you loose too much chlorine to sunlight before the CYA has a chance to build up?
    If you add chlorine to water with high PH is there a danger of staining or just that the chlorine would not be as effective until the PH is lower?

    Thanks
    poolschoolgrad

    20x40 free-form IG vinyl, 1hp Hayward superpump, Hayward pro grid DE filter, Raypak heatpump, Goldline Aquarite SWCG, Polaris 280 with booster, and tested using a Taylor K2006.

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    Re: Reclaiming the pool from algae

    Would there be a problem with using granular tri chlor for a couple of days to maintain the pool to shock level?
    The tri chlor would lower the PH quickly and within a couple of days raise the CYA?
    In theory, that's not a bad idea but won't work too well in a practical sense

    1. Buying small quantities of tri-chlor (tabs) can be a hassle

    2. More important, it will lower the pH much too slowly (it needs to come down now) and will add CYA a little too slowly as well. Easier and more practical to lower the pH with muriatic acid and set the CYA so he gets to 30ppm in just a few days.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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