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Thread: The hierarchy of pool chemistry

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    cubgirl's Avatar
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    Cool The hierarchy of pool chemistry

    Hi Everybody!

    I came to TFP initially because my 5-year-old pool was in serious trouble and I was totally lost! So I read and read and lurked and lurked. I've stabilized my pool now and here's how I categorize the chems & processes in my head. Feel free to correct any errors. (Remember one month ago, I knew practically nothing!)

    THE CHEMS

    The Difficult-To-Lower Chems (Add chemical to Raise and physically replace water to Lower):
    • Salt - aka NaCl (Water Softener Salt/Pellets to raise; replace h2o to lower)
    • Cyanuric Acid - aka CYA (Stabilizer to raise; replace h2o to lower)
    • Calcium Hardness - aka CH (Calcium Chloride to raise; replace h2o to lower)
    • Borates (Boric Acid or (Borax + Muriatic Acid) to raise; replace h2o to lower)

    The "Sort Of" Difficult-To-Lower Chem (Add chemical to Raise and manipulate water environment to Lower)
    • Total Alkalinity - aka TA (Baking Soda to raise; Muriatic Acid/Dry Acid to lower (which also lowers pH) AND then aeration to raise pH

    The "Not Too Difficult"-To-Raise-Or-Lower Chems (Add chemical to Raise and Lower OR just "Wait-It-Out" to Lower)
    • pH (Borax, Soda Ash or Aeration to raise; Muriatic Acid or Dry Acid to lower)
    • Free Chlorine - aka FC (Liquid Clorine, Bleach or Lithium Hypochlorite to raise; lowers over time OR SWCG + Salt to raise; lowers over time)

    THE RELATIONSHIPs

    It's important to know that some of the "Not-Too-Difficult"-To-Raise-Or-Lower Chems work in conjunction with some of the "Difficult"-To-Lower or "Sort Of Difficult"-To-Lower Chems:
    • CYA stabilizes FC (too much CYA creates FC/Algae problems; too little CYA and FC succumbs to sunlight & dies)
    • TA buffers pH (too much TA raises pH and scale will form; too little TA causes pH to fluctuate rapidly (aka pH "Bounce"))

    THE PROCESSES

    OK, so when starting out, know these things:
    • New-fill water may have little to no Salt, none to some Borates, no CYA and no FC.
    • It will, however, have pH, CH and TA levels right out of the tap.
    • First thing to do is to get a good test kit (e.g. Taylor K-2006 --> http://www.amazon.com/Taylor-Complet.../dp/B0002IXIIG).

    For a new-fill Fresh Water Pool:
    1. Add CYA (Using Stabilizer, raise CYA from 0 to 40 - 70 ppm)
    2. Add Chlorine for CYA level (Using Liquid Chlorine, Bleach or Lithium Hypochlorite, raise chlorine from 0 to 16 - 28 ppm for specific CYA levels; see chart --> http://www.troublefreepool.com/conte...art-slam-shock.
    3. Perform Overnight Chlorine Loss Test (OCLT); see here --> http://www.troublefreepool.com/conte...loss-test-oclt
    4. If OCLT test is passed, let chlorine level drift down for CYA level, i.e., 5 - 8 ppm, (see above chart) and maintain these levels.

    For a new-fill Salt Water Pool:
    1. Buy a Salt water test kit --> http://www.amazon.com/TAYLOR-TECHNOL...5290079&sr=1-5
    2. Add Salt to the level required by your SWCG (e.g., 3000 to 4000 ppm)
    3. Add CYA (Using Stabilizer, raise CYA from 0 to 60 - 80 ppm)
    4. Add Chlorine for CYA level (Using Liquid Chlorine, Bleach or Lithium Hypochlorite, raise chlorine from 0 to 24 - 31 ppm for specific CYA levels; see above chart).
    5. Perform Overnight Chlorine Loss Test (OCLT); see here --> http://www.troublefreepool.com/conte...loss-test-oclt
    6. If OCLT test is passed, let chlorine level drift down for CYA level, i.e., 4 - 6 ppm, (see above chart) and maintain these levels.

    Next, for both Fresh & Salt Water Pools:
    1. Get TA to an ideal level (80-120 ppm).
    2. Adjust pH (up or down) as necessary.
    3. Test FC & pH on daily basis - adjust as necessary.
    4. Test CYA, CH and Salt on a weekly basis.
    5. Test TA twice per week, more frequently if you're having pH problems.
    6. Learn to use the Pool Calulator to determine the proper levels --> http://www.troublefreepool.com/calc.html

    Bonus! For extra sparkley water:


    REMEMBER! Using anything but Bleach/Liquid Chlorine/Lithium Hypochlorite (or SWCG) for chlorination will affect your CYA and CH levels! Use these only if you also want to adjust the chemical that's bound to the Chlorine. (Dichlor and trichlor are bound to CYA so they will add CYA and lower pH. Cal-hypo is bound to Calcium and it will add CH.)
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    JasonLion's Avatar
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    Re: The hierarchy of pool chemistry

    Great start.

    Recommended TA with a SWG is between 60 and 80. Recommended CYA level with a SWG is 70 to 80. There is no need to shock/SLAM fresh fill water (unless it comes from a pond). Pool Calculator is now called PoolMath.
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    Re: The hierarchy of pool chemistry

    That's very good. My only corrections/suggestions are the following. There usually are no borates in fill water. Fill water from a tap (not a well) usually does have either FC or CC (monochloramine). The TA recommended range for SWCG pools is 60-80 where often one needs to be on the low end of that range for greater pH stability. For a non-SWCG pool it's 70-90+ but again one usually doesn't need 100 ppm or more TA unless one uses an acidic source of chlorine such as Trichlor tabs (and we don't recommend that; at least not all the time). CYA, CH and Salt don't change very often so even monthly testing is OK unless you've got a leak or massive rain overflow. For borates, we recommend 50 ppm, not 80 ppm. I would say that "Dichlor and Trichlor have chlorine bound to CYA ... Cal-Hypo has chlorine bound to calcium ...
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    Re: The hierarchy of pool chemistry

    My SWCG company recommends TA between 80 to 120, based on Saturation Index and CYA between 60 to 80. Understand there's no FC or CC in tap water (never claimed there was) but what about municipalities that have naturally soft water? What's making it soft?

    chem geek: "The TA recommended range for SWCG pools is 60-80 where often one needs to be on the low end of that range for greater pH stability."

    I thought higher TA = pH stability?

    P.S. Thanks for the correction on the Cal-Hypo being bound to Calcium. I fixed it.
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    Re: The hierarchy of pool chemistry

    You can't mix the advice here with that from manufacturers or pool stores. So if you are writing a summary, please use our recommendations not theirs.

    What I wrote about tap water was that there IS either FC or CC in it. If it's chlorinated tap water, then there will be FC; if it's chloraminated tap water, then there will be CC. You wrote:

    New-fill water may have little to no Salt, none to some Borates, no CYA and no FC.
    I'm saying that is usually wrong. New fill water, unless from a well, usually does have some FC or CC so just leave that last part out of your sentence above.

    Municipalities with soft water have lower CH (calcium hardness) as well as lower magnesium since it is the sum of both that are normally counted as Total Hardness. Water that is not hard is soft. As for what makes it soft, the real question is what makes water hard. Rain water is naturally soft (i.e. it does not contain calcium or magnesium). What makes water hard is when water dissolves minerals in rock, specifically calcium and magnesium. So water from reservoirs filled from rain water direct runoff is usually soft while that which comes from water traveling long distances over rocks and especially going through underground aquifers may be hard.

    No, higher TA is not necessarily better pH stability. You correctly wrote "too much TA raises pH". Basically, TA performs TWO distinct functions. It buffers pH which means the pH is more stable (changes less) from chemical additions that would otherwise move the pH, BUT TA is itself a source of rising pH itself via the outgassing of carbon dioxide. TA is a measure mostly of bicarbonate and pool water is over-carbonated. So while a higher TA will resist changes in pH from chemical additions better, it will also tend to make the pH rise faster on its own (i.e. without adding any chemicals). It's only when using net acidic chemical sources such as Trichlor tabs, Dichlor, or MPS non-chlorine shock, that having a higher TA makes sense since then the carbon dioxide outgassing that has the pH rise counteracts the lowering of pH from these chemical sources so you get reasonable pH stability.
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    Re: The hierarchy of pool chemistry

    Correction - aeration raises pH without doing anything to TA. Adding muriatic acid lowers pH and TA.

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    Re: The hierarchy of pool chemistry

    Quote Originally Posted by cubgirl View Post
    Understand there's no FC or CC in tap water (never claimed there was) but what about municipalities that have naturally soft water?
    I have city water and it has 1ppm of FC. If you have well water then you shouldn't have any chlorine.
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    Re: The hierarchy of pool chemistry

    Quote Originally Posted by Abigail K View Post
    Correction - aeration raises pH without doing anything to TA. Adding muriatic acid lowers pH and TA.
    Hi,

    Everywhere on TFP they instruct to lower TA, you have to lower pH to 7.0-7.2 then aerate to raise pH and lower TA.

    - - - Updated - - -

    Quote Originally Posted by chem geek View Post
    You can't mix the advice here with that from manufacturers or pool stores. So if you are writing a summary, please use our recommendations not theirs.
    I don't talk to pool store people. I did a quick study here & summarized what I learned. Will tweak my post.

    Thanks
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    Re: The hierarchy of pool chemistry

    Abigail K has it right. You need both aeration and acid for it to work, but technically it is the acid which lowers TA. If you raise PH in any other way (besides aeration) it won't work.
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    Re: The hierarchy of pool chemistry

    The following chart shows the TA lowering procedure and how each step affects pH and TA. It is the acid addition that lowers both the pH and the TA. The aeration raises the pH with no change in TA.

    PROCEDURE .......... pH .. TA
    ===================

    Acid ....................... - ..... - ... Lower pH to 7.0 ( or next to lowest measurement on pH test kit, but not below 6.8 )

    Aeration ................ + ..... 0 ... Waterfalls, fountains, showers, point returns up, splash, run SWG
    Acid ....................... - ..... - ... When pH from aeration rises to 7.2, add acid to lower to 7.0
    -----------------------------------
    Aeration + Acid ...... 0 ..... - ... Repeat the above until the TA gets to your target ( e.g. 80 ppm )

    Aeration ................ + ..... 0 ... Aerate (and no longer add acid) until pH rises to target pH ( e.g. 7.7 )

    ===================
    Net Result .............. 0 ..... - ... Net result is lowering TA with no change in pH ( unless final pH target is different than starting pH )
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    Re: The hierarchy of pool chemistry

    One other thing, many/most water supplies contain some salt naturally, amounts of a few hundred ppm is not uncommon.
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