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Thread: Optimal Chemistry Levels

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    Question Optimal Chemistry Levels

    As a new owner of an in-ground, SWG spa, I spent some time perusing the recommendations in the Pool School area regarding optimal chemical levels. However, the recommended levels in my IntelliChlor Electronic Chlorine Generator manual are considerably different (based upon APSP standards). I would appreciate some insight in the discrepancy. Thank you kindly.

    Pool School

    FC: 4 - 6ppm
    pH: 7.5 - 7.6
    TA: 60 - 80ppm
    CH: 350 - 450ppm
    CYA: 70 - 80

    IntelliChlor Manual
    FC: 2 - 4ppm
    pH: 7.2 - 7.8
    TA: 80 - 120ppm
    CH: 200 - 400ppm
    CYA: 30 - 50ppm
    Kit
    14' X 11' rectangular in-ground spa; 2,360 gals; plaster/gunite; SWCG (Pentair IntelliChlor); Pentair Intelliflo varaible-speed pump; EasyTouch4 control system; cartridge filters; auto cover

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    JoyfulNoise's Avatar
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    Re: Optimal Chemistry Levels

    Quote Originally Posted by Kit View Post
    As a new owner of an in-ground, SWG spa, I spent some time perusing the recommendations in the Pool School area regarding optimal chemical levels. However, the recommended levels in my IntelliChlor Electronic Chlorine Generator manual are considerably different (based upon APSP standards). I would appreciate some insight in the discrepancy. Thank you kindly.

    Pool School

    FC: 4 - 6ppm
    pH: 7.5 - 7.6
    TA: 60 - 80ppm
    CH: 350 - 450ppm
    CYA: 70 - 80

    IntelliChlor Manual
    FC: 2 - 4ppm
    pH: 7.2 - 7.8
    TA: 80 - 120ppm
    CH: 200 - 400ppm
    CYA: 30 - 50ppm
    Many of those levels are based on industry practices going back as much as 40 years with little or no basis in real science.

    For example, the APSP will tell you all you need is 2-4ppm FC, full-stop. That is completely wrong as the optimal FC level depends on your CYA concentration as CYA both protects FC from UV but, more importantly, acts as a chlorine buffer that substantially lowers the concentration of hypochlorous acid (active chlorine that kills pathogens and oxidizes bather waste) to levels that allow you to swim in the water. If your CYA is too high and your FC is too low, then there will not be enough active chlorine in the water to kill pathogens and you'll get an algae bloom.

    As for CYA, your IntelliChlor manual must be an older version. All of the newer online versions of the IntelliCHlor owner's manual has the CYA concentration between 50-80ppm as Pentair has come to realize that SWG's operate much more efficiently at higher CYA levels.

    As for TA, again that is based on industry lore. It was believed that metals would be protected when water contained higher levels of carbonate alkalinity as a passive layer of carbonate would form on metal surfaces. That is totally bogus and it's an idea that was ripped off from the water boiler sciences which deals with a completely different type of water system (closed water systems). There's is also the belief by the industry that the higher carbonate alkalinity more strongly buffers the water against pH dropping. That may be true in some circumstances BUT, with any form of water aeration, high levels of carbonate alkalinity will result in increasing pH levels due to carbon dioxide outgassing. Once again, the industry completely misunderstands or ignores the science of water-carbonate chemistry.

    CH levels are mostly irrelevant for vinyl pools and, in plaster pools have very wide ranges. My pool has over 800ppm CH and I run an SWG as well...guess what, I NEVER get calcium scale.

    TFP Recommended levels are based on science and the experience of tens of thousands of TFPC practitioners. We teach people how to maintain their pools properly by revealing and simplifying the science behind pool water chemistry. We teach our members how to test their own water so they can rely on themselves and we teach our members all about the everyday (and CHEAP) chemicals they can use to keep their pools clean, clear and perfectly sanitized.

    Welcome to TFP

    Best wishes,
    Matt
    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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    JoyfulNoise's Avatar
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    Re: Optimal Chemistry Levels

    In case you did not find this while looking through the TFP forums, here is a very well written and informative post that details what is taught to Certified Pool Operators by the APSP and details what they get right and what they get wrong -
    Certified Pool Operator (CPO) training -- What is not taught

    If you have any specific information you would like to discuss, you are certainly welcome to post a question in our forums. However, there is a Search box in the upper right corner of the TFP web-pages that uses a Google plug-in to search all of TFP. You can basically type in any search term in that box (use double quote "" around groups of words you want to keep together, ex "water chemistry" ) and you will get lots of results. I often find that I can type a few words in that box and 99% of the time find a thread that discussed my exact question.

    Once again, welcome!
    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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    Join Date
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    Medford, Oregon
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    Re: Optimal Chemistry Levels

    Matt,

    Thank you for the thorough & thoughtful response. I can appreciate that fact that "national standards" can often be rather generic, outdated & (at times) tempered by risks of litigation. Although I am not a chemist, the rationale behind some of the recommendations regarding target chemical levels on this website certainly seem logical. So, having said this, I will use the levels advocated here for my spa.

    Thank you also for the link to the article.

    Kit
    Kit
    14' X 11' rectangular in-ground spa; 2,360 gals; plaster/gunite; SWCG (Pentair IntelliChlor); Pentair Intelliflo varaible-speed pump; EasyTouch4 control system; cartridge filters; auto cover

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    Mod Squad pooldv's Avatar
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    Re: Optimal Chemistry Levels

    I think you can use this procedure and just use the SWG as the main source of chlorine and supplement with bleach as needed.
    How do I use Chlorine in my Spa (or pool)?
    TFP Moderator
    If TFP helped you or saved you money - Become a TFP Supporter! <--Click here
    2012 build and pics, 20k gal gunite, black onyx pebblesheen, OK flagstone, IntellifoVS, cart filter w/Pleatco, IC40 SWG, Solartouch, 5 12'x4' solar panels, HP50HA heat pump, 8mil solar cover, borates, TF-100 test kit, SONOS, Doheny's Discovery Robot, hot tub on bleach

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    Re: Optimal Chemistry Levels

    Good, useful read. Thank you so much.

    Kit
    Kit
    14' X 11' rectangular in-ground spa; 2,360 gals; plaster/gunite; SWCG (Pentair IntelliChlor); Pentair Intelliflo varaible-speed pump; EasyTouch4 control system; cartridge filters; auto cover

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