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Thread: Difference in TA levels

  1. Back To Top    #1

    Join Date
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    Difference in TA levels

    Hi,

    I am new to this forum and to pool ownership. We just put a new saltwater pool in last summer.

    My question is why are the TA levels from this forum for SWGs (60-80) so different from my manufacturers and the pool store (80-120)? The chlorine levels are higher here too......3-5 versus 1-3.

    I also have an ozone generator that they added to get my business! Should my chemical levels be adjusted for this?

    Thank you,
    Madeline
    10,620 gallons/IG/plaster
    SWG
    Cartridge Filter
    Ozonator (only because PB wanted my business!)
    Pump 1.5 HP (2-speed)

  2. Back To Top    #2

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    Re: Difference in TA levels

    Basically, many industry outlets have not kept up with the science behind pool water management as well as others have.

    We recommend a lower TA oftentimes because it is easier to control pH rise that accompanies the use of a SWCG. The slightly higher FC with an SWCG is recommended as such because we know by experience that these levels are appropriate in that the operator experiences the least amount of problems with algae and other organics in the water. It is also easier on the cell since you don't have to run the cell at such a high output to keep up with the chlorine that is consumed. We also know that based on the level of CYA that is recommended for SWCG operators, that 3 ppm of FC is the bare minimum to be safe.

    You shouldn't need to adjust an chemical levels because of your ozonator.
    10K gallon IG gunite with waterfall; Pentair CC320P filter; WhisperFlo 2 HP pump
    TF Test Kits - Pool Math - Pool School
    "It depends."- JohnT

  3. Back To Top    #3

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    Re: Difference in TA levels

    In a nut shell, the lower TA is recommended to counter act the upward pressure that a SWCG puts on the pH. Through a few mechanisms, the generator will cause the pH to rise a little faster than a pool chlorinated using other means. A lower TA will counteract that rise and, a a result, not as much acid will have to be added to the pool on a regular basis. You can keep a TA in the 80-100 range, but you will have to add more acid here and there to keep the pH in line.

    The chlorine question is a bit more complex. What the pool stores don't understand is the relationship between chlorine and stabilizer or cyanuric acid (CYA). There are smarter chemist types on here that can explain it better, but the upshot is that CYA binds the chlorine, holding it in reserve. So..with CYA in the water, a free chlorine (FC) level of 4-5 ppm with a CYA level of 40-50 is actually like having an FC less than 1. If you have any stabilizer in the water at all (>20 ppm) an FC of 1-3 will be borderline at best to keep algea from growing in the pool. The 1-3 ppm FC number given by the pool industry really only apply to an indoor pool with no CYA at all.

    EDIT: 257 is a faster typist than me
    14,000 gallon IG, Vinyl. Hayward 3/4 hp superpump, Penatair IC40 SWCG, Pentair automation, Hayward sand filter, Aqua Comfort heat pump, Hayward 400k Lo-Nox LP heater.

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    Re: Difference in TA levels

    So THAT'S why I have been having to put so much Muratic Acid in my pool lately!! I really didn't have to put that much in at the beginning, but I can't seem to get it below 8 now! So now I will have to lower my TA (110). Thank you both so much......and I actually (kinda) understand what you are talking about! These pool store people like talking over one's head!!!

    Thanks again!

    Madeline
    10,620 gallons/IG/plaster
    SWG
    Cartridge Filter
    Ozonator (only because PB wanted my business!)
    Pump 1.5 HP (2-speed)

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    Re: Difference in TA levels

    Hi Maddie,

    There's an article in Pool School for How to Lower Alkalinity.

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    Re: Difference in TA levels

    Maddie,

    The responses to your questions in this thread have been absolutely outstanding and are a testament to the education that this site provides to people with pools and spas. Also, your curiosity and wanting to understand the recommendations in Water Balance for SWGs is admirable.

    The concept of a lower TA actually resulting in more pH stability is one of the most counter-intuitive concepts in all of pool water chemistry. The reason for the confusion is that a higher TA has TWO different effects that compete with each other. A higher TA results in greater pH buffering, meaning that it takes a greater addition of acid or base to move the pH a given amount. However, TA is also a SOURCE of rising pH itself because TA is mostly a measure of the carbonation level in the pool and pools are intentionally over-carbonated. So a higher TA level results in faster carbon dioxide outgassing and that results in a faster rise in pH. This latter effect is the dominant one so lowering the TA level usually results in a slower rate of pH rise and also results in less acid being needed over time.

    There are two other factors that can lower the amount of acid you need to use, but I'd lower your TA first since it's best to make one adjustment at a time in your pool so you can isolate, understand, and tweak each effect separately. The rate of pH rise from carbon dioxide outgassing is faster at lower pH, so setting a somewhat higher pH target of 7.6 to 7.7 instead of always trying to hit 7.5 or lower is also helpful and what we recommend. Obviously, the use of a pool cover would virtually eliminate the outgassing and is another approach one can take that also significantly reduces water loss from evaporation and the resulting rise in both TA and CH that can result from these quantities that are present in fill water. Finally, one can add 50 ppm Borates to the pool which acts as an additional pH buffer but without the side effect of carbon dioxide outgassing (i.e. it is not a source of rising pH) and also acts as a mild algaecide that sometimes lowers the chlorine usage letting you turn down the SWG on-time even further.

    The chlorine and CYA relationship is known science since at least 1974, but has been virtually ignored by the industry in terms of recommendations for FC levels in pools and spas which should really be dependent on the CYA level. We recommend a high 60-80 ppm CYA level in SWG pools to reduce the amount of chlorine broken down by the UV in sunlight since that lets one turn down the SWG on-time resulting in a longer cell life and also reducing the rate of pH rise since some of that rise is related to the SWG itself. At 80 ppm CYA, one really needs 4 ppm FC to prevent algae growth, even in pools that are rich in algae nutrients. Chlorine alone can prevent algae growth, but the active chlorine level needs to be high enough and that level is roughly determined by the FC/CYA ratio so a higher CYA level needs a higher FC level to have the same amount of active chlorine. A pool with 4 ppm FC and 80 ppm CYA has roughly the same active chlorine level as a pool with only 0.05 ppm FC and no CYA. Fortunately, it takes a very low active chlorine level to kill pathogens and prevent algae growth.

    Richard
    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: Difference in TA levels

    Quote Originally Posted by Maddie
    So THAT'S why I have been having to put so much Muratic Acid in my pool lately!! I really didn't have to put that much in at the beginning, but I can't seem to get it below 8 now! So now I will have to lower my TA (110). Thank you both so much......and I actually (kinda) understand what you are talking about! These pool store people like talking over one's head!!!

    Thanks again!

    Madeline
    Yeppers, and you actually have a couple of things to contend with as far as your pH rise is concerned. Not only do you have a highish TA and a SWCG, both of which cause the pH to increase, but you also have plaster that is less than one year old. Plaster can take up to a year to fully cure. During the curing process, the pH can rise fairly significantly. The good thing about this is that after a year, you won't have to contend with the plaster curing component as it will settle down.
    10K gallon IG gunite with waterfall; Pentair CC320P filter; WhisperFlo 2 HP pump
    TF Test Kits - Pool Math - Pool School
    "It depends."- JohnT

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    Re: Difference in TA levels

    Ah! How appropriate! I got the from the pool stores when I told them the numbers I was trying to achieve and was curious to see why it was so different than the numbers they recommend. I got the "well you can't believe everything you read on internet" as well..

    That information was well worth my "lifetime supporter" fee to this forum!
    19.5k gallons in ground, P4 panel with turbocell SWG, 1hp Hayward superpump II, sand filter, Heater low nox 250k btu heater, solar cover on rocky roller

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