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Thread: pH 7.0 and FC 0.4 - SWG

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    HardTrance9's Avatar
    Join Date
    Oct 2009
    Los Cabos

    pH 7.0 and FC 0.4 - SWG


    Today we tested another of the pools (in my signature marked as GM) using a "borrowed" Pentair test kit (pH and Chlorine only).

    This SWG pool is one I commented in other thread that had some algea problem and I was thinking/asking here if it could be because of having very low "dirty" quality water from the "street" directly to the pool.

    So finally we could test at least the pool (the kit ran over before we could test the water) and this is what we got:

    I don't if FC would be the same as saying just "Chlorine"?

    pH 7.0 target 7.5
    FC 0.4 target 1.5
    Pool capacity: 10,028.55 gallons
    Pool surface: plaster
    Pool get sunlight directly, BUT in this case, it has been raining not very hard over here for the last 4 days, no sun at all.

    After consulting the Pool Calculator from here, got the conclusion that we need to add 700 g. or 25 Oz. of Soda Ash/Washing Soda (this is one thing available at this place for now; just taking over all the pools on my signature)
    in order to raise pH by 0.53 and also TA by 18 (don't know at all what our TA level is, no way to measure it for now).

    This would theoretically put the pH on 7.53

    Also, to "fix" the Chlorine 0.4 (FC?), the calculator said that we should add 2.7 oz. or 75 g. of Dichlorine in order to raise the FC by 1.1, lowe pH by 0.04 and raise Salt by 1 (also don't know at all what the current Salt level could be for now).

    This would theoretically put the FC on 1.5 and the pH adjusted to 7.49

    Does this sounds ok for you?

    I know that there are many additional considerations, but it's the first attempt (of many I think) to find out why this pool is the worse of all three

    We will test again tomorrow but unfortunately we kit ran over... tomorrow we should have sunlight again.
    In charge of some SWG and Bleach pools... still a newbie..

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    duraleigh's Avatar
    Join Date
    Apr 2007
    Sebring, Florida

    Re: pH 7.0 and FC 0.4 - SWG

    Almost surely, the pool needs to be shocked. The chlorine is virtually nonexistant......probably because the algae is consuming it. 1.5ppm chlorine will have little effect....the algae will quickly consume that and you'll be right back where you started.

    Read "How to shock your pool" in Pool School. YOu will find you'll likely have to bring your FC up to a very high level (and that all depends on your CYA level) to defeat the algae. Importantly, you will have to HOLD the FC at that very high level by constantly replenishing the chlorine.

    Before you start, you really need to get a good test result for your CYA (stabilizer) level. Test strips are woefully inadequate for that purpose....they are ok for a couple of things but are just too undependable to accurately test for CYA.

    Once you get your CYA test result, folks here can tell you just how much FC is required to adequately shock the pool. Keep reading and asking questions.....this stuff is puzzling at first but it will be second nature to you very soon.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    frustratedpoolmom's Avatar
    Join Date
    May 2007
    SWSuburban Chicago, IL

    Re: pH 7.0 and FC 0.4 - SWG

    You state your "target is 1.5".... your kit is measuring Total Chlorine not Free Chlorine.

    Your target is based on your CYA level. Until you know that - you don't know your target.

    I agree with Dave, you need to shock the pool, with liquid chlorine if you can get it. At the minimum your Shock level is going to be 10 FC - but depending on your current CYA level it could be much higher.

    Dichlor will raise the CYA level - I wouldn't use it unless you can confirm the CYA is below where it needs to be for your pool.
    Helpful links: Pool School; CYA/Chlorine Chart
    24' round AG pool, 52" high, Raypak heater; Waterway 2 spd Pump;
    150 Sq ft. Clearwater Cartridge Filter; Former and DISSATISFIED "Pool Frog" owner
    Perfectly Clear Pool Service, Find me on Facebook!

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    HardTrance9's Avatar
    Join Date
    Oct 2009
    Los Cabos

    Re: pH 7.0 and FC 0.4 - SWG

    Ok, many thanks for your insights.

    Actually the kit bottles say "pH" and "OTO" (chlorine/bromine)...

    Ok I will ready the "how to shock..."

    Ordering now one TF-100 kit for this SWG pool...

    Thanks and will keep reading and posting.. thanks for your help.
    In charge of some SWG and Bleach pools... still a newbie..

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