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Thread: will Liquid Chlorine Raise pH?

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    will Liquid Chlorine Raise pH?

    Moderator Note: Split from this thread - can muriatic acid and baking soda be added to pool at the same time? - Page 3


    Quote Originally Posted by JamesW View Post
    The 80 to 120 rule is based on incorrect information. It is not a useful guideline to follow. I would suggest that you base the TA on how the ph moves. If the ph rises, the TA is probably too high. If the ph drops, the TA is probably too low. When the ph remains stable, the TA is just right.
    But what about the addition of chlorine? Isn't it suppose to raise pH?

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    Re: can muriatic acid and baking soda be added to pool at the same time?

    Trichlor lowers ph and total alkalinity. Salt systems and bleach are mostly ph neutral when accounting for chlorine usage.

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    Re: can muriatic acid and baking soda be added to pool at the same time?

    Quote Originally Posted by JamesW View Post
    Trichlor lowers ph and total alkalinity. Salt systems and bleach are mostly ph neutral when accounting for chlorine usage.
    Is there any link where this is explained and justified in detail?

    I mean, everybody (including pool experts) has the notion that liquid chlorine will raise pH. Is this a myth?

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    will Liquid Chlorine Raise pH?

    Quote Originally Posted by kouroubel View Post
    Is there any link where this is explained and justified in detail?

    I mean, everybody (including pool experts) has the notion that liquid chlorine will raise pH. Is this a myth?
    It isn't a myth per se, it is just based on a complete misunderstanding of chlorine chemistry. Adding bleach to water can cause a temporary increase in pH which is usually offset by the chlorine reacting with organics and biological matter which are acidic (creates a proton) reactions. Thus, on balance, the net chlorine reactions are pH neutral. Most retail and commercial liquid chlorine products contain a small excess of lye from the manufacturing process but this amount of OH- is minimal and does not change the pH with normal levels of liquid chlorine use. If one were to add significant amounts of bleach (for example, raising the pool water chlorine concentration to shock levels), then the pH rise would need to be offset by an initial lower of the pH with acid. This is why TFP requires a pool owner to adjust their pH down to 7.2 prior to starting a SLAM.

    Most of the pool industry (both chemical and operations) is based on a lot of old notions that are founded on anecdote rather than facts. Little of what the pool industry "recommends" has changed in the last 30 years. If you're interested in the detailed chemistry, see these posts written by Richard Falk (aka, chem geek) -

    Pool Water Chemistry

    Certified Pool Operator (CPO) training -- What is not taught

    Chlorine/CYA Chart

    Degradation of Cyanuric Acid (CYA))

    pH Buffer Capacity

    And Mark (aka mas985) has written extensively about pumps and hydraulics -

    Hydraulics 101 - Have you lost your head?
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    Re: can muriatic acid and baking soda be added to pool at the same time?

    Quote Originally Posted by kouroubel View Post
    I mean, everybody (including pool experts) has the notion that liquid chlorine will raise pH. Is this a myth?
    It is becoming more common to see this myth busted, as it's only 1/2 true. Even in the link you listed earlier
    they too agree this is simply not true,

    They initially raise the pH of the water but when free chlorine is used, it creates an equal amount of acid so the net effect on pH is zero.

    As Matt stated, adding liquid chlorine DOES increase the pH at first, however as it's used up the acid that's created lowers it back down to where it was before......thus equaling each other out making it pH neutral.

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    Re: will Liquid Chlorine Raise pH?

    If also seen it explained that people are used to tabs, which are more acidic, so switching to something pH neutral makes it seem like it raises th pH.
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