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Thread: PH going down ... why?

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    nthoms's Avatar
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    PH going down ... why?

    My water still looks great ... that's the good news.

    However ... my PH is dropping. It was hovering at 7.2, now it's barely reading 7.0

    FC: 5.0
    CC: 0.2
    TC: 5.2
    PH: 7.0
    TA: 70
    CH: 60
    CYA: 45
    SALT: 2900
    TEMP: 82
    SATURATION: -1.37

    Any advice on my next steps ... I am concerned about the PH being below (7.0). Should I be?
    22,500 gallon, vinyl lined, cartridge, salt water pool

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    Butterfly's Avatar
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    Re: PH going down ... why?

    Are you running the SWG? If yes, then the pH should be maintained in the mid 7's.

    It sounds like you are using something acidic, like trichlor pucks. ????
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    Patrick_B's Avatar
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    Re: PH going down ... why?

    Yes, your pH should be at least 7.2

    Where are you getting these results If you don't me asking? I'm curious because of the 5 and 0.2 FC readings displayed.
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    nthoms's Avatar
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    Re: PH going down ... why?

    Quote Originally Posted by Butterfly View Post
    Are you running the SWG? If yes, then the pH should be maintained in the mid 7's.

    It sounds like you are using something acidic, like trichlor pucks. ????
    I am using a SWG.
    22,500 gallon, vinyl lined, cartridge, salt water pool

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    nthoms's Avatar
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    Re: PH going down ... why?

    Quote Originally Posted by Brushpup View Post
    Yes, your pH should be at least 7.2

    Where are you getting these results If you don't me asking? I'm curious because of the 5 and 0.2 FC readings displayed.
    I am using the FAS-DPD K-2006 kit.
    22,500 gallon, vinyl lined, cartridge, salt water pool

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    JasonLion's Avatar
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    Re: PH going down ... why?

    Any chance the PH test reagent is going bad? I would only consider that possibility if it is more than 18 months old.

    Otherwise, are there any other chemicals being added to the pool, perhaps sequestrant?
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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    nthoms's Avatar
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    Re: PH going down ... why?

    Quote Originally Posted by JasonLion View Post
    Any chance the PH test reagent is going bad? I would only consider that possibility if it is more than 18 months old.

    Otherwise, are there any other chemicals being added to the pool, perhaps sequestrant?
    I thought the same thing so I bought new reagent ... unfortunately it tested the same

    And, no, I have not added anything to the water.
    22,500 gallon, vinyl lined, cartridge, salt water pool

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    Mod Squad jblizzle's Avatar
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    Re: PH going down ... why?

    Well, pH does not drop on its own ... especially with a SWG. So, this is a head scratcher

    What is the pH of your tap water?
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    Re: PH going down ... why?

    Could it have anything to do with CYA being lower than recommended for SWG?
    21K gallon, plaster, 1hp Hayward MaxFlo pump, Hayward 244s sand filter, 3/4 hp Halcyon PB4-60Q booster pump, Polaris 280 cleaner.

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    Re: PH going down ... why?

    Quote Originally Posted by rterickson View Post
    Could it have anything to do with CYA being lower than recommended for SWG?
    That has nothing to do with pH. In fact, one could argue that the lower CYA requires the SWG to run more and thus raise the pH more.
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    Re: PH going down ... why?

    Perhaps you need to bump your TA up just a bit to 80 and see if that helps it stabilize. Or raise CH.

    I'll admit that I am over my head with the chemistry but were this a plaster pool it would be pulling calcium from the plaster to get into balance.
    23,000 gallon in ground pool with rock waterfall and spillover spa, Aqualink control system, Polaris 380 cleaner, Purex Triton Clean&Clear Plus cartridge filter. Located in The Woodlands, Texas.

    Pool owner since Nov 2008, Trouble Free since April 2009. Happy to help when I can.

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    Re: PH going down ... why?

    The only thing that I can think of would be cyanuric acid. If you haven't added any, then it seems odd for the pH to drop.

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    Re: PH going down ... why?

    Acid rain maybe?
    How do you have a CH of 60? My city fill water is 3 times higher than that.
    How long does it take to drop from 7.2 to 7.0?
    I find my pH holds fairly steady @ 80 TA. Maybe you could bump it up some. With a lower TA, pH will drop faster than with a higher TA.
    It has to be some kind of acid being added to your pool somewhere.
    18,000 Gallon Aboveground. Sand Filter with 2HP 2 speed Pump.

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    Re: PH going down ... why?

    Something else is going on here. I'm curious about Jason's question on the fill water pH.
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    Re: PH going down ... why?

    My PH went from 7.2 to 7.0 in about a three week period of time ... we had a lot of rain during that time and I probably drained about 3" of water off the pool.

    I haven't had to fill my pool in years ... I rely totally on rain water. I drain down about a foot of water each Fall when I close the pool and then the winter rain and snow will fill it back up.

    I added stabilizer yesterday to try to bring my CYA up a bit. Am I correct in understanding that adding stabilizer will also contribute to lowering PH?

    So is the consensus among the experts that I should raise my TA?

    - - - Updated - - -

    Quote Originally Posted by anonapersona View Post
    Perhaps you need to bump your TA up just a bit to 80 and see if that helps it stabilize. Or raise CH.

    I'll admit that I am over my head with the chemistry but were this a plaster pool it would be pulling calcium from the plaster to get into balance.
    I have a 22,500 gallon, vinyl lined, cartridge filtered, salt water pool. There (hopefully) is no plaster involved
    22,500 gallon, vinyl lined, cartridge, salt water pool

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    Re: PH going down ... why?

    1. Putting your city and state in your sig helps us understand your climate.

    2. I see no reason to change your TA

    3. Monitor your pH and keep it 7.2 - 7.8 or so.

    4. Be thankful you are a unique (and I mean unique) pool that pH lowers 99.9999% slowly go up.

    5. Check your pH fill water....that seems the only logical answer.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
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    Re: PH going down ... why?

    Quote Originally Posted by duraleigh View Post
    1. Putting your city and state in your sig helps us understand your climate.
    Colchester, Connecticut

    Quote Originally Posted by duraleigh View Post
    2. I see no reason to change your TA
    Quote Originally Posted by duraleigh View Post
    3. Monitor your pH and keep it 7.2 - 7.8 or so.
    So does this mean I should add something (?) to increase the PH ?

    Quote Originally Posted by duraleigh View Post
    4. Be thankful you are a unique (and I mean unique) pool that pH lowers 99.9999% slowly go up.
    Quote Originally Posted by duraleigh View Post
    5. Check your pH fill water....that seems the only logical answer.
    22,500 gallon, vinyl lined, cartridge, salt water pool

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    Re: PH going down ... why?

    So does this mean I should add something (?) to increase the PH ?
    Yes. 20 Mule Team Borax. Dose per PoolMath in upper left corner of every page..
    Dave S.
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    Re: PH going down ... why?

    I had this problem until this year. I was having to adjust the pH upward by 0.5 at least once every two weeks. I kept my pool covered with solar disks alot and thought that may have been contributing, but his year I have a solar blanket and it's not happening. The only thing I have done differently is keep a much higher TA. (Last two years 70-80, this year 110) Like you, I have a very low CH (50), so that makes me wonder if our low CH is somehow related. I found that in the five years I kept tropical fish here, that my pH in tanks was much more stable after adding crushed coral to the same low CH water I am putting in the pool.
    5K gal, 16'X4' Intex Ultra AG, Intex 3in1 - 55 lb Sand Filter, SWG, 1600 GPH (Model-CS15110), T-100
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    Re: PH going down ... why?

    Quote Originally Posted by Amy.M View Post
    I had this problem until this year. I was having to adjust the pH upward by 0.5 at least once every two weeks. I kept my pool covered with solar disks alot and thought that may have been contributing, but his year I have a solar blanket and it's not happening. The only thing I have done differently is keep a much higher TA. (Last two years 70-80, this year 110) Like you, I have a very low CH (50), so that makes me wonder if our low CH is somehow related. I found that in the five years I kept tropical fish here, that my pH in tanks was much more stable after adding crushed coral to the same low CH water I am putting in the pool.

    Thanks so much for this info ... I will try raising my CH. this weekend.
    22,500 gallon, vinyl lined, cartridge, salt water pool

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