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Thread: TA / Ph Roller coaster

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    TA / Ph Roller coaster

    After almost 10 years using an undersized cartridge filter, I installed a big sand filter last June. Love the beast, EXCEPT for two things. Ever since then, pool water has been noticeably cloudy and I CANNOT get my TA & Ph under control. Since it's winter time, thought I'd worry about the cloudiness in the spring and focus on getting my chemistry stabilized. Wild fluctuations in both TA & Ph. For example, yesterday morning I measure the Ph - it's off the charts high. Blood red on the color chart. TA is VERY (~20) compared to last weekend. I like to get my Ph in range before I tackle the TA, so I add a 1/2 gallon of muratic acid. Remeasure the Ph in the afternoon and it's still a little high, TA still very low, so I add another 1/4 gallon of muratic acid and let it sit over night. Get up this morning and Ph is REALLY low (like maybe 6.7) and TA like 10. So I add about 12 pounds of baking soda. 4 hours later, TA is at 60 but Ph is sky high again - same blood red on the color chart. I've repeated this cycle about twice a month since I got the sand filter. Chlorine and CA are rock solid (~ 4.5 and 40 respectively). Any suggestions?
    16,000 gal in-ground Pebble-tec pool / Pebble-sheen spa. Jandy AquaPure 1400 SW Cl gen (SWG) system. In-floor cleaning system w/ Hayward EcoStar 2.0 HP VSP pump. Hayward 31" sand filter. 900 sq ft Heliocol solar panels (on roof) w/ separate 1 HP Pentair WhisperFlow single speed pump. Water feature with separate Hayward 0.85 HP VSP pump.

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    Re: TA / Ph Roller coaster

    Low TA will result in quick pH swings. Try keeping the TA at 60 or higher while you bring down the pH. (Add baking soda to raise TA, wait an hour, add muriatic acid to lower pH which of course will lower TA, too.)

    Does the TA appear to be dropping without you adding acid? Or do the acid additions explain the low TA?
    Outdoor 14,000 gallon IG plaster pool built in 2000 with spillover spa, 2 hp WhisperFlo pump with MagneTek motor, Sta-Rite cartridge pool filter with 300 ft2 filtration area and 0.33 gpm/ft2 filtration rate, Aquabot Rapids 4WD robotic pool cleaner, Raypak digital gas heater, and Intermatic mechanical timer located in the Dallas-Fort Worth metroplex

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    Mod Squad zea3's Avatar
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    Re: TA / Ph Roller coaster

    Your SWG will raise pH over time. You will need to raise the TA higher than normal so you have room to lower the pH and have both values in range. Raise the TA to around 120 then lower the pH to 7.5 When you are finished the TA should be between 70-120. Try not to let the TA drop below 70. Most pools have a TA they "like" that keeps the pH fairly stable. Once you get the TA back up it will be easier to find the best TA for your pool. Use the poolmath button to calculate how much baking soda and MA to add for each adjustment.
    TFP Moderator
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    Vogue 21' round AG, Pentair 1 hp 2 speed pump, 36 sq ft DE filter, Hayward S180T 150# sand filter, Houston, Texas
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    Re: TA / Ph Roller coaster

    For an SWG pool, you usually need the TA on the low side so around 70 ppm. If you have it higher, then the rate of pH rise will be faster. When you add acid, it lowers both pH and TA, but for the TA to drop as much as you indicate you must be adding a lot of acid. 41 fluid ounces of full-strength Muriatic Acid (31.45% Hydrochloric Acid) in 16,000 gallons would drop the TA by 10 ppm, but starting at 70 ppm the pH would drop from 8.0 to 7.13. Also note that you'll use more acid more frequently if you try and keep the pH lower -- try a 7.8 target instead of 7.5 and don't lower the pH so much when you do add acid. That is, see how your pool does with a TA of 70 ppm and a pH of 7.8. Does it rise in pH as quickly? Do you use as much acid to maintain it?

    Some people add 50 ppm Borates to their pool to reduce the frequency of acid addition. The borates buffer the pH without having the side effect of carbon dioxide outgassing that causes the pH to rise (the bicarbonate that comprises of most of TA outgases carbon dioxide causing the pH to rise). Do you have a lot of aeration sources in your pool such as waterfalls, spillovers, fountains, etc.? If so, see if you can reduce their on-time if possible.

    I'm not sure why switching to a sand filter caused this problem -- that part doesn't make much sense.
    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
    12 Fafco solar panels; Purex Triton PowerMax 250 natural gas heater (200,000 BTU/hr output); automatic electric pool safety cover; 4-wheel pressure-side "The Pool Cleaner"

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    Re: TA / Ph Roller coaster

    Your testing methods (what kit are you using?) may reveal some helpful information.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
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    Re: TA / Ph Roller coaster

    Wow - thanks for all the great advice. Let me try and answer the questions. First - it does not look to me like the TA varies much if I haven't tried something with the Ph. I was getting the TA to about 70 and then adding muratic acid to get the Ph in range, without success. When I was too busy to mess with this, the TA stayed around 70 with the Ph very high. This past weekend the TA was about 70 (maybe lower) when I added a bunch of acid and that drove the TA to near zero. I am using the TF test kit for the TA test and the standard Taylor drop test for the Ph test. The TF kit is old (~ 3 years). I was planning to buy a whole new kit in the spring. I just bought a new Taylor Ph vial (from Leslie's so who knows how fresh it is). I also agree that I don't see the connection between going from a cartridge to a sand filter would be part of this problem. I was routinely adding muratic acid because of the SWG, but before the sand filter the TA rarely moved off 90. So from all the advice it appears to me that I've not gotten the TA high enough before trying to bring the Ph down. I will get the TA higher before trying to lower the Ph and let you know the results. Thanks again for all the tips.
    16,000 gal in-ground Pebble-tec pool / Pebble-sheen spa. Jandy AquaPure 1400 SW Cl gen (SWG) system. In-floor cleaning system w/ Hayward EcoStar 2.0 HP VSP pump. Hayward 31" sand filter. 900 sq ft Heliocol solar panels (on roof) w/ separate 1 HP Pentair WhisperFlow single speed pump. Water feature with separate Hayward 0.85 HP VSP pump.

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    Mod Squad Bama Rambler's Avatar
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    Re: TA / Ph Roller coaster

    You shouldn't need to be adjusting the TA at all. If you're purposefully raising the TA, you're just fighting yourself. I suspect your reagent is bad and giving you a false reading. I think I'd get some TA reagent and see what it shows.

    P.S. No guarantees but, Dave usually puts the TF-100 complete refill kit on sale in the spring so you may want to just get some TA reagent right now and wait to get the refill.
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/¼hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
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    Re: TA / Ph Roller coaster

    P.S. No guarantees but, Dave usually puts the TF-100 complete refill kit on sale in the spring
    It'll start on March 5 this year.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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