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Thread: SWG and high bather load, and SWG math

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    tdp's Avatar
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    Question SWG and high bather load, and SWG math

    Hi all, I have a Hayward T-9 SWG for a ~16K gal. pool. I know that SWG's only put out a small amt. of chlorine at a time. How do you other SWG owners handle a high bather load? Do you use bleach to get a quick FC spike before the pool party or right after, or do you just turn up your SWG? Also, I have the spreadsheet from TFP called SWG_Settings.xlsx that gives me the output of ounces by weight of chlorine gas produced; how do you translate that to FC?

    FC 4
    CC 0
    CYA 80
    pH 7.5 (although that pH test is awfully hard to read, for me at least)
    TA 70
    CH 220

    Thanks!!
    ~17,500 gal. IG Fiberglass, Viking "Cambridge"; installed 6/2015
    SWG Hayward Turbo Cell T-9
    Hayward Hi-Rate Sand Filter
    Hayward Max-Flo XL pump
    TF-100 Test Kit/SpeedStir

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    Mod Squad pooldv's Avatar
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    Re: SWG and high bather load, and SWG math

    Hold the PH test in full light in front of a light background. White paper plate, concrete deck, light sky, etc.

    Yes, we always bump FC up before a big swim day and after. My CYA is 80 and I keep FC about 8 ppm, a jug of 8.25% bleach adds 4 ppm of FC in our pool so I add a jug before. If FC isn't still at 10ish after then I'll add another after. Remember it is safe to swim with FC up to shock level for your CYA, FC/CYA Chart
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    needsajet's Avatar
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    Re: SWG and high bather load, and SWG math

    Per its specs, your chlorinator puts out 0.7 lbs of chlorine per 24 hours. Your weight of pool water is gallons times 8.35 (rounded, ignoring TDS and temperature).

    PPM is 'Pounds of chlorine' divided by 'pounds of water' times 1,000,000.

    The FC we test and talk about is expressed as units of chlorine gas (Cl2)
    12k IG salt; glass beads in plaster; K-2006C, K-1766, CCL, and Aussie 4in1 (HTH); Pentair Eco800 1.2HP VS; Zodiac SWC 1.3 lb/day (25 g/hr); 25" filter recycled glass; OKU solar panels; 1/2 HP solar pump; Rebel (Warrior) pool cleaner; FlowViz; prior pool AG 10k | Read Before Posting to get the best possible advice | ... and this helped me a lot!: TFPC for Beginners

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    tdp's Avatar
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    Re: SWG and high bather load, and SWG math

    Quote Originally Posted by needsajet View Post
    Per its specs, your chlorinator puts out 0.7 lbs of chlorine per 24 hours. Your weight of pool water is gallons times 8.35 (rounded, ignoring TDS and temperature).

    PPM is 'Pounds of chlorine' divided by 'pounds of water' times 1,000,000.

    The FC we test and talk about is expressed as units of chlorine gas (Cl2)
    What is TDS?

    So that means for a 17K pool, I could expect my SWG to put out ~4.9 PPM FC per 24 hrs. if turned up to 100%? That's really useful information--thank you!


    ~17,500 gal. IG Fiberglass, Viking "Cambridge"; installed 6/2015
    SWG Hayward Turbo Cell T-9
    Hayward Hi-Rate Sand Filter
    Hayward Max-Flo XL pump
    TF-100 Test Kit/SpeedStir

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    needsajet's Avatar
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    Re: SWG and high bather load, and SWG math

    TDS is total dissolved solids, mostly salts, which increase the density of water. Conversely, warmer water is less dense than colder water when above 4 degrees C. These aspects are not relevant to pool management, but saying 8.35 lbs per gallon is simplified, so I noted the simplification.
    12k IG salt; glass beads in plaster; K-2006C, K-1766, CCL, and Aussie 4in1 (HTH); Pentair Eco800 1.2HP VS; Zodiac SWC 1.3 lb/day (25 g/hr); 25" filter recycled glass; OKU solar panels; 1/2 HP solar pump; Rebel (Warrior) pool cleaner; FlowViz; prior pool AG 10k | Read Before Posting to get the best possible advice | ... and this helped me a lot!: TFPC for Beginners

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