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Thread: Creeping pH due to my pool chemistry?

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    Creeping pH due to my pool chemistry?

    Here are my readings via Taylor test kit:
    pH - 7.6
    FC - 5.5-7 (depending on time of day)
    CYA - 40
    TA - 60
    CH - 300
    BO - 30
    Temp - 85 deg F

    No severe problems in pool (water is clear) but I have constantly creeping pH (up) and am adding muriatic acid frequently. I'm thinking of increasing the borates up to 50 or so and adding sodium bicarb to bring the TA to 80 or 90.

    Any suggestions or feedback?
    In-ground plaster pool, ~18,500 gal, Hayward single-speed pump, Pentair 60 sq. ft. DE filter, Polaris 280 robotic cleaner, SPA, heater (seldom used), use Taylor K2006 series test kit

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    pwrstrk's Avatar
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    Creeping pH due to my pool chemistry?

    How frequently are you adding acid ? Once a week, more than once a week ? Do you have a lot of water features ?
    Jeff
    24'x54" AG Morada RTR (by wilbar) 13'500 gal. Hayward Powerflo Matrix 1hp 2 speed. Hayward Perflex EC65 DE filter.

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    Mod Squad woodyp's Avatar
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    Re: Creeping pH due to my pool chemistry?

    7.6 is fine. Might bump up your TA a bit to help.
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    Re: Creeping pH due to my pool chemistry?

    Quote Originally Posted by pwrstrk
    How frequently are you adding acid ? Once a week, more than once a week ? Do you have a lot of water features ?
    And how old is the pool?
    33' round, 23,000 gal AG vinyl , 1HP 2spd PowerFlo Matrix downsized with 3/4HP impeller (X2), Hayward S180T 150# sand filter (X2), Hayward H250 NG heater Pool Store year 1 - $850 for 2 months; Pool Store year 2 - $440 for 2 months, TFPC year 1 - $170 for 4 months; TFPC year 2 - $95 for 4.5 months
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    Re: Creeping pH due to my pool chemistry?

    Do you have a SWG? I have similar numbers (but CYA of around 60), and my slowly creeping pH got worse when I added my SWG earlier this summer. I need to add around 1/2 gallon of the 15% muriatic acid weekly to keep the pH between 7.5 and 7.8. Raising CYA might help, but I don't see why adding bicarbonate to raise TA would.
    ___________________________________
    10K gal, plaster, SWG, DE filter, solar heat

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    Mod Squad woodyp's Avatar
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    Re: Creeping pH due to my pool chemistry?

    " but I don't see why adding bicarbonate to raise TA would."

    Because TA acts to help buffer PH from rapid rises.............
    16x32x52" Steel Cornelius Miramar AGP Vinyl liner 13,100 gal. Buried 2 ft.
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    Re: Creeping pH due to my pool chemistry?

    Most pools tend to rise in pH as well. Its not uncommon.
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    Re: Creeping pH due to my pool chemistry?

    I add acid (1-2 pints) about once every 10 days or so. The pool is 25 years old but appears to have been replastered. The plaster is getting pretty badly pitted. I have a spa so there is some CO2 outgassing from the small fountain and the small waterfall. That would tend to lower the carbonic acid in the pool and raise the pH. That's my current thinking, at least. I read that bleach also raises the pH. I don't have a SWG.

    I'm thinking of adding 10# of sodium bicarb to raise the alkalinity and 20# of either borax of a product of borax and acid that is balanced, do these things slowly in stages, and monitor the pH and bring it back down with muriatic acid. I am hoping this added buffer will stabilize the pH a bit. That's my plan. Comments or advice?
    In-ground plaster pool, ~18,500 gal, Hayward single-speed pump, Pentair 60 sq. ft. DE filter, Polaris 280 robotic cleaner, SPA, heater (seldom used), use Taylor K2006 series test kit

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    Smykowski's Avatar
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    Re: Creeping pH due to my pool chemistry?

    Given the size of your pool and your water features (aka aeration), I see nothing to worry about.
    33' round, 23,000 gal AG vinyl , 1HP 2spd PowerFlo Matrix downsized with 3/4HP impeller (X2), Hayward S180T 150# sand filter (X2), Hayward H250 NG heater Pool Store year 1 - $850 for 2 months; Pool Store year 2 - $440 for 2 months, TFPC year 1 - $170 for 4 months; TFPC year 2 - $95 for 4.5 months
    The most important article on this site - The ABCs of Pool Water Chemistry

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    Re: Creeping pH due to my pool chemistry?

    Quote Originally Posted by eswayze
    Raising CYA might help, but I don't see why adding bicarbonate to raise TA would.
    Quote Originally Posted by woodyp
    Because TA acts to help buffer PH from rapid rises.............
    At pH 7.6, bicarbonate is a pretty good buffer for pH decreases (which is what the TA test measures), but not nearly as good at buffering pH increases. So I would argue the buffering effect of increased bicarbonate/CO2 concentration would be pretty small for muting pH rises. Borates would do better for muting pH increases. However, increasing either buffer concentration won't change the total acid demand of the pool. With increased buffering capacity, the pH rise may be slower over time, but in the end more acid will be needed to get the pH back down. I suggested increasing CYA since if evaporative loss of Cl2(g) is the cause of the pH increase, added stabilizer will help.
    ___________________________________
    10K gal, plaster, SWG, DE filter, solar heat

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    Re: Creeping pH due to my pool chemistry?

    Quote Originally Posted by woodyp
    Because TA acts to help buffer PH from rapid rises.............
    If the pH is rising in a pool due to carbon dioxide outgassing, then increasing the TA NEVER helps and actually hurts by increasing the rate of pH rise. The higher TA the higher the amount of carbon dioxide in the water and the faster the rate it will outgas and that causes the pH to rise. The use of a non-carbonate buffer such as borates will normally slow down the rate of rise, but will not lower the total amount of acid that needs to be added. This is because it increases pH buffering, but does not fundamentally solve the core problem which is too much carbon dioxide in the water.

    The simple thing to remember is that though TA is a pH buffer, it is also a SOURCE of rising pH in its own right. So increasing TA usually only makes sense if the pH tends to fall or if the TA is quite low so has the saturation index be quite negative. A rule of thumb is that 60 ppm TA is the lowest without borates and 40 ppm with borates, though this will also depend somewhat on the CYA level (but as a rough rule of thumb it's a reasonable floor for TA). If needed, the calcium hardness (CH) and pH target can be higher to prevent the saturation index from becoming too negative.

    Quote Originally Posted by pool_dufus
    I add acid (1-2 pints) about once every 10 days or so. The pool is 25 years old but appears to have been replastered. The plaster is getting pretty badly pitted. I have a spa so there is some CO2 outgassing from the small fountain and the small waterfall. That would tend to lower the carbonic acid in the pool and raise the pH. That's my current thinking, at least. I read that bleach also raises the pH. I don't have a SWG.

    I'm thinking of adding 10# of sodium bicarb to raise the alkalinity and 20# of either borax of a product of borax and acid that is balanced, do these things slowly in stages, and monitor the pH and bring it back down with muriatic acid. I am hoping this added buffer will stabilize the pH a bit. That's my plan. Comments or advice?
    By the way, 1-2 pints every 10 days or so is not a lot of acid in a 18,500 gallon pool. If you wait until your pH is higher before you add acid, that may lessen the amount you need to add if the pH rise is due to carbon dioxide outgassing. This is because there is more carbon dioxide outgassing at lower pH. So if you were to only add your 3 cups of acid after the pH went to 7.8, then that would lower it to 7.5. This chart shows the amount of over-carbonation in a pool at various pH and TA levels.

    I had a period of time in my pool, which is covered most of the time so should have minimal carbon dioxide outgassing, where the pH was rising faster than normal and I was adding a pint every week or two to 16,000 gallons. That has since stopped and I think it was during a period where the pool was going through bursting of calcium nodules so having more exposure to calcium hydroxide under improperly bonded plaster. Perhaps your pool is going through something similar, though actual pitting is not a good sign and usually indicates the saturation index is too low. Yours is currently at around -0.2, but if you add enough acid to get your pH down to 7.3 (3 cups would do that from 7.6), then that's a saturation index of -0.5 which with a "poor plaster" job might be too low, especially over a longer period of time.

    The fountain and waterfall would indicate aeration may be at least part of the source of pH rise so if that is the case I would NOT raise your TA. Increasing the borates to 50 ppm may help slow down the rate of rise a little (though not the amount of acid you add over time), but quite frankly you'd notice more of a difference going from no borates to some and you already have some. Also try targeting 7.8 before you add acid and don't go below 7.5 after doing so. If you plan to keep the TA this low permanently, you might consider bumping up your CH to 400, though that's not critical.
    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: Creeping pH due to my pool chemistry?

    I would suggest maintaining the pH at 7.8 instead of 7.6. This will help reduce pH rise from carbon dioxide offgassing by lowering the amount of CO2 in the water. It will also help raise your CSI to neutral, which would help reduce plaster degradation. Plaster degradation will raise the pH and TA due to calcium carbonate in the plaster being dissolved into the water.

    Do you typically get clouding when you brush the pool?

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    Re: Creeping pH due to my pool chemistry?

    @JamesW - No, I do not notice clouding when brushing the pool. There may sometimes be a minimal amount, but its small enough to be just accumulated dust and debris. So answer is no, not really.

    I inherited this pool 2 years ago and it was already pitted when I got it. I do not know the history of the pool, or when it was last plastered. On some of the edges of the steps concrete can be felt where the plaster is totally gone. Other places on the wall the plaster is pitted. So, it is quite possible that the pool has been mistreated for many years ... no way to know.

    What I'm hearing in summary is DON'T increase the TA, maybe bump the borates up to 50 but don't expect much effect, keep the pH a little higher at 7.8, and perhaps run the CH up to 400. Don't I risk scaling with such a high CH?? Any down side for a pH this high (eye irritation, for example?)?
    In-ground plaster pool, ~18,500 gal, Hayward single-speed pump, Pentair 60 sq. ft. DE filter, Polaris 280 robotic cleaner, SPA, heater (seldom used), use Taylor K2006 series test kit

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    Re: Creeping pH due to my pool chemistry?

    You could maintain a higher pH or increase CH some, but not both. You can check your CSI using the poolcalculator.com. if you have iron issues, then a higher ph might increase the risk of staining, but otherwise a ph of 7.8 won't be a problem. Don't raise TA.

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    Re: Creeping pH due to my pool chemistry?

    Thanks to all. I will go with the slightly higher pH.

    (Different subject) What would help me most here is a lower water temp and less UV, in terms of bleach consumption. Will fall never come to Texas? It's eating close to two quarts a day (8.5% bleach) these days with 103 deg. air temps and full sun all day. Water temp runs 85-87 degrees, close to being uncomfortable for swimming. I have some left-over dichlor tablets I may use to help contribute to the chlorine level and up the CYA a tad. I'm still well below 50.
    In-ground plaster pool, ~18,500 gal, Hayward single-speed pump, Pentair 60 sq. ft. DE filter, Polaris 280 robotic cleaner, SPA, heater (seldom used), use Taylor K2006 series test kit

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    Re: Creeping pH due to my pool chemistry?

    Quote Originally Posted by pool_dufus
    It's eating close to two quarts a day (8.5% bleach) these days with 103 deg. air temps and full sun all day.
    That is pretty good actually...I would expect more like 3 quarts per day with no swimmers and no other organics if the pool is in the sun most of the day with 40 ppm cya. You could up cya to 50 ppm and that would probably reduce you chlorine consumption a little, but like I said, you are already doing quite well.
    TFP Expert who uses Pool School and my TF100 test kit along with PoolMath for my: Round 11K gallon AGP with deep end, 20" sand filter, Matrix 1hp 2spd, 6 2ftX20ft solar panels (and solar cover!), Intex SWCG (copper bars disconnected) and a Rubadub hot tub (chlorine). The SLAM process is not finished until: 1. CC < 0.5 ppm, 2. An OCLT < 1.0 ppm and, 3. The water is crystal clear.

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