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Thread: Saturation Index

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    nthoms's Avatar
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    Saturation Index

    Please take a look at my chart below ... I am concerned about the Saturation Index. What should I do to help bring the Saturation Index back in-line?

    As always, your help is greatly appreciated

    [attachment=0:uyl9fjna]PoolChemistry6.29.2013.jpg[/attachment:uyl9fjna]
    22,500 gallon, vinyl lined, cartridge, salt water pool

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    Richard320's Avatar
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    Re: Saturation Index

    Who cares? You have a vinyl pool. There's no danger of plaster etching.

    If you're obsessive, run the pH in the upper half of the comfort zone 7.5>7.8 and it should be fine.

    What's important is: How does the pool look? Clear? Sparkly? No dry skin? No frizzy hair? No burning eyes? That's what's important. Nobody outside this board gives a hoot whether your numbers are perfect, but they'll sure notice perfect water.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
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    Re: Saturation Index

    NT,
    I'd be much more concerned about the 1.6 and 2.4 on your last two FC readings.
    Are you flirting with disaster?
    Alan
    Alan in Wellington, FL - near West Palm Beach
    15,200 gal IG, painted plaster, 1988; 200 SqFt cartridge filter, 2013; 1.5 HP 1-speed pump (uprated), 2005; heat pump, 2005;
    soon to repair (dead) SWG AquaRite T-15 cell, 2005, and replace (dead) suction-side cleaner, 2005.
    Almost everything died this winter 2012-'13, and I know we shouldn't complain... but, Arrgh!

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    nthoms's Avatar
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    Re: Saturation Index

    @Richard

    I was concerned about the cement around my pool, fiberglass steps, and metal ladder ... when I saw that the saturation index indicated corrosive I got concerned.

    My pool water looks good. I've suffered for so many years with bad water (cloudy, algae, iron stains) This is my first year doing all this "testing" and I'm still trying to understand what it all means.

    Sorry ... I guess I truly don't really understand all this pool Chemistry stuff ... I'm still trying to learn

    But thanks for your "candid" reply.
    22,500 gallon, vinyl lined, cartridge, salt water pool

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    nthoms's Avatar
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    Re: Saturation Index

    Quote Originally Posted by alanpaul
    NT,
    I'd be much more concerned about the 1.6 and 2.4 on your last two FC readings.
    Are you flirting with disaster?
    Alan
    Between the two readings I had shocked the pool so the 2.4 is coming down from a decent shock (12+) ... I will raise it today back up.

    Thanks
    22,500 gallon, vinyl lined, cartridge, salt water pool

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    Richard320's Avatar
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    Re: Saturation Index

    Quote Originally Posted by nthoms
    I was concerned about the cement around my pool, fiberglass steps, and metal ladder ... when I saw that the saturation index indicated corrosive I got concerned.

    My pool water looks good. I've suffered for so many years with bad water (cloudy, algae, iron stains) This is my first year doing all this "testing" and I'm still trying to understand what it all means.

    Sorry ... I guess I truly don't really understand all this pool Chemistry stuff ... I'm still trying to learn

    But thanks for your "candid" reply.
    Yeah, I should have put a smiley in there.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
    A pool is like a pet - you have to feed it every day, even the days you don't want to play with it!

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    nthoms's Avatar
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    Re: Saturation Index

    Quote Originally Posted by Richard320
    Quote Originally Posted by nthoms
    I was concerned about the cement around my pool, fiberglass steps, and metal ladder ... when I saw that the saturation index indicated corrosive I got concerned.

    My pool water looks good. I've suffered for so many years with bad water (cloudy, algae, iron stains) This is my first year doing all this "testing" and I'm still trying to understand what it all means.

    Sorry ... I guess I truly don't really understand all this pool Chemistry stuff ... I'm still trying to learn

    But thanks for your "candid" reply.
    Yeah, I should have put a smiley in there.
    So it's safe to say that I don't need to pay any attention to the SI?

    Just keep plugging along keeping my numbers within range?
    22,500 gallon, vinyl lined, cartridge, salt water pool

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    Re: Saturation Index

    I don't really understand CSI but I did notice that your tests seem to be about a week apart. Do you test more often and this just doesn't show that? I would think that might be a tad long between tests? The risks of going for days on end with less than ideal numbers can be scary....
    My Amazon Smile for November12K Fiberglass IG, Infinity 4000 automatic cover, SWCG, Hayward Sand Filter, Hayward 1.5 Pump, Doheny Discovery Robot, Savi Melody LED pool lights, outdoor speakers and other assorted doo-dads. Sundance Altamar Hot Tub.
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    Richard320's Avatar
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    Re: Saturation Index

    Quote Originally Posted by nthoms
    So it's safe to say that I don't need to pay any attention to the SI?

    Just keep plugging along keeping my numbers within range?
    Yep. http://www.poolcalculator.com/chemistry.html#CSI
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
    A pool is like a pet - you have to feed it every day, even the days you don't want to play with it!

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    Re: Saturation Index

    The cement around the pool is not constantly immersed in water. It also gets rained on and the rain likely has a very negative saturation index due to near zero calcium hardness (CH). It will wear on the concrete, but not quickly. Low pH is much more detrimental as it accelerates the rate of dissolving, not just whether it can dissolve at all. If you are concerned about your concrete, I suggest you seal it. We have troweled concrete that we seal every year with Glaze 'N Seal Multi-Purpose Sealer. We seal because of weathering, not splash-out.
    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
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    Re: Saturation Index

    Quote Originally Posted by chem geek
    The cement around the pool is not constantly immersed in water. It also gets rained on and the rain likely has a very negative saturation index due to near zero calcium hardness (CH). It will wear on the concrete, but not quickly. Low pH is much more detrimental as it accelerates the rate of dissolving, not just whether it can dissolve at all. If you are concerned about your concrete, I suggest you seal it. We have troweled concrete that we seal every year with Glaze 'N Seal Multi-Purpose Sealer. We seal because of weathering, not splash-out.
    Wow, thank you for the information. It's exactly the comments I was looking for. I've become proficient at testing the water, but I'm still trying to learn what it all means and what the impact of each component is.

    I've kept the PH low because it seems like when I raise the PH I start to get metal (iron) staining on my fiberglass steps. Any insights??? Or suggestions???
    22,500 gallon, vinyl lined, cartridge, salt water pool

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    Re: Saturation Index

    Quote Originally Posted by YippeeSkippy
    I don't really understand CSI but I did notice that your tests seem to be about a week apart. Do you test more often and this just doesn't show that? I would think that might be a tad long between tests? The risks of going for days on end with less than ideal numbers can be scary....
    I test with my kit every Saturday ... in between those tests I will test with strips (but I don't record those).
    22,500 gallon, vinyl lined, cartridge, salt water pool

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    Re: Saturation Index

    Quote Originally Posted by nthoms
    I've kept the PH low because it seems like when I raise the PH I start to get metal (iron) staining on my fiberglass steps. Any insights??? Or suggestions???
    Your pH is usually around 7.4 which is fine and the lowest was 7.0. When I say low pH with regards to concrete, I'm talking about lower than that. I wouldn't worry about the splash-out. You can seal it for general weathering -- good sealants also protect the concrete somewhat from sunlight as well, but that mostly applies to colored concrete.

    Do you use a metal sequestrant? If so, it needs to be added every week or two in a maintenance dose since chlorine will slowly break it down. If you aren't using a metal sequestrant and are just preventing the pH from getting too high, that's fine and up to you -- it's just a little risky if you lapse and the pH gets high.

    Having some CH in the water, usually around 150 ppm or so, does seem to help against cobalt staining, but I'm not sure about iron staining. The good news is that iron stains are the easiest to remove -- a little ascorbic acid does the trick. You can learn more by reading the Pool School article Metals in the Water and Metal Stains.
    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
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    Re: Saturation Index

    nthoms,

    In your sig you mention a salt water pool but does that include a SWCG? It is a little easier to maintain a clean cell if the CSI is slightly negative.
    Mark
    Hydraulics 101; Pump Ed 101; Pump/Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, MaxFlo SP2303VSP, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

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    Re: Saturation Index

    Quote Originally Posted by mas985
    nthoms,

    In your sig you mention a salt water pool but does that include a SWCG? It is a little easier to maintain a clean cell if the CSI is slightly negative.
    Yes, I do have a SWCG. When you say "slightly negative" ... do my SI numbers qualify as "slightly negative"?
    22,500 gallon, vinyl lined, cartridge, salt water pool

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    mas985's Avatar
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    Re: Saturation Index

    I try to keep mine between 0 and -0.5 but I have a plaster pool so I don't want to get the CSI too low. But in your case, I think the numbers are fine.
    Mark
    Hydraulics 101; Pump Ed 101; Pump/Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, MaxFlo SP2303VSP, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

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