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Thread: Adding Bleach Raises pH Slightly

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    Adding Bleach Raises pH Slightly

    I've been using 8.25% bleach as my chlorine source for the last couple of weeks after coming out of a situation in which CYA got too high after trying to combat an algae problem. I now use a TF-100, and the CYA/chlorine chart said to keep FC around 6 with my current CYA level of 50. Each time I add more bleach to get my FC level up, it raises my pH as well. I'm concerned about raising my pH too high. I've never had to lower my pH (challenge has always been keeping it up to a good level), but if I start using muriatic acid to lower it, will that affect my FC level?
    23,000 gal. IG gunite pool, DE filter, elevated spa with spillover, Polaris 280 cleaner

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    Re: Adding Bleach Raises pH Slightly

    I don't think it is as much the bleach raising the ph as it is the lack of the ph lowering effects your previous chlorine source had (I am guessing trichlor pucks). Your ph tends to increase with time due to swimming and splashing, so needing to lower your ph occasionally is not a big deal.

    Good luck!
    21.5K gal, vinyl, ?? HP Jacuzzi pump, sand filter

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    Re: Adding Bleach Raises pH Slightly

    Thanks! I've never had to get muriatic acid before. Where is the best place to get it? Is there a particular brand that I should look for (or avoid!)?
    23,000 gal. IG gunite pool, DE filter, elevated spa with spillover, Polaris 280 cleaner

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    Re: Adding Bleach Raises pH Slightly

    I get mine at the local hardware store. Just make sure you are getting 20 baume and be careful with it. It's some pretty serious stuff!
    21.5K gal, vinyl, ?? HP Jacuzzi pump, sand filter

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    Patrick_B's Avatar
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    Re: Adding Bleach Raises pH Slightly

    First, how high is your FC when you are testing pH? Also, I assume you are using the color block (phenol red) pH kit? High Chlorine gives false high pH on that test. Can we see a full set of numbers please? Bleach pH is high, but the conversion and breakdown is a net acid reaction. It wont raise your pH long term.
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    Re: Adding Bleach Raises pH Slightly

    When you increase the FC level using a hypochlorite source of chlorine (bleach, chlorinating liquid, Cal-Hypo, lithium hypochlorite), the pH will rise. However, when the FC drops back down from the chlorine being used/consumed, the pH will drop back down as well. Over time, a pH rise usually comes from carbon dioxide outgassing and that occurs more if the Total Alkalinity (TA) is higher, so what is your TA level? Perhaps you need to lower it some.

    Also, it is not uncommon to have to add some acid every now and then. If your TA isn't too high, you may only need to add it once a week or two or perhaps even less. If you need to add it more frequently, then your TA is probably too high or you have significant water aeration sources (fountains, waterfalls, spillovers, etc.).
    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: Adding Bleach Raises pH Slightly

    Below are my test numbers from last night:

    FC = 3 (added bleach last night, now FC = 7)
    CC = 0.5
    TA = 80
    CH = 140
    CYA = 50
    pH = 7.5

    I didn't realize that my chlorine was so low (I had been testing this week, but I'm still getting used to the TF-100 and forgot that you're supposed to multiply by 0.5 when you do the Chlorine Drop Test - feel like an idiot), so I added some bleach last night which brought my FC up to a 7 this morning.

    The low chlorine level that I've had all week certainly explains the greenish tint that had come back to my water, so I added more bleach today to bring the water up to shock level. Chlorine/CYA chart said my shock level is 20. According to the Pool Calc., I only had enough bleach on hand to bring FC up to 18, so that's what I've just done. Hopefully that works to clear up the water. Is it likely that I'll have to add acid to lower the pH after putting so much bleach in?
    23,000 gal. IG gunite pool, DE filter, elevated spa with spillover, Polaris 280 cleaner

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    Mod Squad jblizzle's Avatar
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    Re: Adding Bleach Raises pH Slightly

    Review the SLAM procedure, it is not a one time elevated FC. You must maintain the FC at shock level until you pass the three criteria to stop.
    Jason, TFP Moderator
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    Re: Adding Bleach Raises pH Slightly

    Is it likely that I'll have to add acid to lower the pH after putting so much bleach in?
    No. Always test pH before you add the chlorine, which you did. Your pH is 7.5 and is perfect. You should not test the pH if FC is above 10, as that will skew the test to a false high reading.

    Your pool is green? You are planning to do the SLAM process?
    TFP Moderator TF100 Test Kit TF100 TestKit YouTube Channel PoolMath
    You're done SLAMing when:
    1)You lose 1ppm or less FC overnight, & 2)You have .5ppm CC's or less, & 3)your water is clear.

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    Re: Adding Bleach Raises pH Slightly

    It's not totally green, but when I was sweeping some debris last night, I started seeing green clouds coming up off of the bottom. It's not feeling slimy. I hoped that increasing the chlorine to shock level would take care of it.
    23,000 gal. IG gunite pool, DE filter, elevated spa with spillover, Polaris 280 cleaner

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    Patrick_B's Avatar
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    Re: Adding Bleach Raises pH Slightly

    Quote Originally Posted by PoolFrog
    It's not totally green, but when I was sweeping some debris last night, I started seeing green clouds coming up off of the bottom. It's not feeling slimy. I hoped that increasing the chlorine to shock level would take care of it.
    Nope, it takes time and exposure to kill it all. It is why we promote the SLAM process, and we don't say go shock you pool like pool stores and pool "pros" say it.

    It is a PROCESS of time and elevated FC until everything is completely killed off. Please read through it and begin one yourself. Sounds like you really need it. Ask questions if you need to but check it out and get a SLAM going.
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    Re: Adding Bleach Raises pH Slightly

    Sweeping or brushing will really help clear up the pool , along with the higher FC levels. Keeping your FC at SLAM levels will vastly improve your results. If you want, you can test every hour as long as the FC is consumed rapidly. If you used a 5 ml sample for your FC testing, you will use half as much reagent but you lose precision.
    -- Guy --
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    Re: Adding Bleach Raises pH Slightly

    Is it safe to swim during the SLAM process if I'm not exceeding shock level of FC?
    23,000 gal. IG gunite pool, DE filter, elevated spa with spillover, Polaris 280 cleaner

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    Re: Adding Bleach Raises pH Slightly

    Quote Originally Posted by PoolFrog
    Is it safe to swim during the SLAM process if I'm not exceeding shock level of FC?
    Yet, as long as the pool is not so cloudy that you could not see a swimmer, up to shock level is fine .
    TFP Moderator TF100 Test Kit TF100 TestKit YouTube Channel PoolMath
    You're done SLAMing when:
    1)You lose 1ppm or less FC overnight, & 2)You have .5ppm CC's or less, & 3)your water is clear.

    ~ One should not use a sledge hammer to swat a mosquito. ~

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