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Thread: SWG Chemistry

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    Join Date
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    SWG Chemistry

    First I just want to reiterate how informative this site is. I just installed a new IG pool last year and I am already more expert on water chemistry than others I know who have had pools all their life. I must say my new pool has indeed been TROUBLEFREE!!!

    My pool was completed late in the season last year so I waited until this season to put in the salt and start up the SWG. I have also followed the SWG chemistry recommendations from this site. My question is that at these recommended levels the Saturation Index in PoolMath is consistently mid-range negative. Meaning around -.3 to -.4. Is this intended? If so why is balanced (index = 0) not good for a SWG?

    Thanks, I'm just concerned about leaving it in negative territory all the time.
    TpoolJ
    36K gal, IG Pebblesheen Aqua Blue, Pentair VS Intelliflo, Pentair DE filter S8D110, PoolPilot Total Contral SWG/PH Feeder, LaMotte ColorQ Pro7, Pentair Propane Heater, Polaris 3900 Sport. Southeastern PA

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    Re: SWG Chemistry

    Those numbers will be perfect and will not degrade the plaster. What they will do is help keep the cell from forming scale and not reducing its lifespan due to the need to clean it with acid when scale forms.
    16k gal plaster with raised spa, Jandy DEV60 filter, 2 HP 2-speed SHPF Jandy Stealth pump
    Hayward Aqua Rite T-15 SWCG, Jandy LXi 400k BTU NG heater, 350 sq.ft. of Sun Star solar panels, TF-100 Test Kit, Dolphin s300i Cleaner
    Test Kits . Pool Math . Chlorine/CYA Chart . The SLAM Process

  3. Back To Top    #3
    JoyfulNoise's Avatar
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    SWG Chemistry

    The water chemistry inside the cell is very different than the bulk pool water. The biggest difference is that the pH is a lot higher inside the cell as the generation and low solubility of hydrogen gas drives up the pH. So, even if your bulk pool water is -0.3, inside the cell is probably closer to 0.

    Can you post your latest test numbers? I'd like to see why your CSI is so negative.


    Matt
    16k IG PebbleTec pool, 650gal spa, spillway and waterfall, 3HP IntelliFlo VS / 1.5HP WhisperFlo, Pentair QuadDE-100 filter, IC40 SWCG, MasterTemp 400k BTU/hr NG heater, KreepyKrauly suction-side cleaner Dolphin S300i robot, EasyTouch controls, city water, K-1001, K-2006 and K-1766 test kits, Mannitol test for borates

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    Re: SWG Chemistry

    The Recommended Levels relating to the CSI for an SWG plaster pool are as follows:

    pH 7.6-7.8 ..... Mid-Range: 7.7
    TA 60-80 ..... Mid-Range: 70
    CH 350-450 ..... Mid-Range: 400
    CYA 70-80 ..... Mid-Range: 75
    assume Salt is 3000 and Temp is 80

    The CSI in PoolMath with the above is -0.14 so where are you getting -0.3 to -0.4? Even if I were to use the mid-ranges in PoolMath set up for "troublefreepool.com", "SWG", and "Plaster" which has pH 7.65, TA 70, CH 300, CYA 75 I get -0.31 so is that what you are talking about? We made changes to the Pool School Recommended Levels tightening up the pH range and moving up the CH range and these changes have not been made to PoolMath yet.
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
    12 Fafco solar panels; Purex Triton PowerMax 250 natural gas heater (200,000 BTU/hr output); automatic electric pool safety cover; 4-wheel pressure-side "The Pool Cleaner"

  5. Back To Top    #5

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    Re: SWG Chemistry

    I found some numbers that don't match our recommendations in this area of Pool School, Pool School - Water Balance for SWGs. We need to have a mod fix these numbers to match the recommendations in chem geek's post above. The pH and CH are a little off.
    16k gal plaster with raised spa, Jandy DEV60 filter, 2 HP 2-speed SHPF Jandy Stealth pump
    Hayward Aqua Rite T-15 SWCG, Jandy LXi 400k BTU NG heater, 350 sq.ft. of Sun Star solar panels, TF-100 Test Kit, Dolphin s300i Cleaner
    Test Kits . Pool Math . Chlorine/CYA Chart . The SLAM Process

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    Re: SWG Chemistry

    I'll echo what ping said - Water Balance for SWGs should be changed to reflect the updated recommendations.

    I'm also wondering why the FC recommendation for CYA = 70-80 was changed (from 4-6 to 3-5)
    23,000 gallons IG gunite, pebble (I think)
    Hayward SP2610X15 1.5 HP Pump, Hayward sand filter
    Mineral Springs SWCG (it's actually Hayward/Goldline), Hayward Goldline T-CELL-15
    Polaris pool cleaner (with booster pump)
    TF-100, SpeedStir, K-1766 Taylor Salt Test, Lamotte Borate test strips

  7. Back To Top    #7

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    Chester Springs, PA
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    Re: SWG Chemistry

    THANKS EVERYONE!
    Here are my current numbers
    FC 4.2
    TC 4.3
    PH 7.8
    TA 77
    CH 240
    CYA 75
    It looks like I should raise my CH. I was around 300 at closing last year, but I had some scale over the winter (new pool was open for only 60 days before closing) that dissolved on its own within weeks of rebalancing/opening. However my Calcium from my readings and the pool store have consistently been around 240 this year and I've been hesitant to raise it because of the scale last year...but I've been told that was because the finish was so new still. I've also kept the PH consistently between 7.6 and 7.8...I'm a little anal about keeping the pool balanced.
    Thanks again for all you help and comments...I've referred a good number of new folks to this site as well.
    TpoolJ
    36K gal, IG Pebblesheen Aqua Blue, Pentair VS Intelliflo, Pentair DE filter S8D110, PoolPilot Total Contral SWG/PH Feeder, LaMotte ColorQ Pro7, Pentair Propane Heater, Polaris 3900 Sport. Southeastern PA

  8. Back To Top    #8

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    Re: SWG Chemistry

    Chem Geek,
    Yes, to your question about -.31 in Poolmath. I've been right around that number all summer. It looks like I need to increase my CH for the new recommendation. Will there be an announcement when Poolmath is updated?
    36K gal, IG Pebblesheen Aqua Blue, Pentair VS Intelliflo, Pentair DE filter S8D110, PoolPilot Total Contral SWG/PH Feeder, LaMotte ColorQ Pro7, Pentair Propane Heater, Polaris 3900 Sport. Southeastern PA

  9. Back To Top    #9

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    Re: SWG Chemistry

    -0.3 is not a serious problem. We changed the Recommended Levels not so much for the mid-range, though that should be closer to -0.2 for SWG pools, but rather for the low-end of the range (except for CYA at the high-end) since that was too low before pushing -0.7
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
    12 Fafco solar panels; Purex Triton PowerMax 250 natural gas heater (200,000 BTU/hr output); automatic electric pool safety cover; 4-wheel pressure-side "The Pool Cleaner"

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