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Thread: Low TC, high TA, High pH in hot tub-how to fix?

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    Default Low TC, high TA, High pH in hot tub-how to fix?

    We just tested our water and the TC is very low, while TA and pH are really high...how can it be so alkaline AND have such high pH (over 8.5) simultaneously? And it says there is almost NO calcium...but I am afraid to add some because it is already so alkaline and basic...what is going on?

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    Default Re: Low TC, high TA, High pH in hot tub-how to fix?

    High pH and high TA go hand in hand.
    Is the fill water also high TA? If not, maybe the easiest thing to do is replace the water.
    Calcium is really only a consideration for concrete / plaster pools.
    12'x24' oval 7.7K gal AG vinyl pool; ; Hayward S270T sand filter; Hayward EcoStar SP3400VSP pump; hrs; K-2006; PF:16

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    Default Re: Low TC, high TA, High pH in hot tub-how to fix?

    Quote Originally Posted by Maggie View Post
    We just tested our water and the TC is very low, while TA and pH are really high...how can it be so alkaline AND have such high pH (over 8.5) simultaneously? And it says there is almost NO calcium...but I am afraid to add some because it is already so alkaline and basic...what is going on?
    What is going on is your water is out of balance...nothing really strange. Easy to fix. A normal part of water maintenance.

    High TA (level of bicarbonate in the water) will lead to high pH because there is a lot of carbonation in the water and the constant aeration found in hot tubs causes CO2 to gas off. Outgassing of CO2 is the primary cause of pH rise in hot tubs and pools. The cure is to lower the TA. You lower TA by adding acid. This also lowers pH. You then aerate which causes pH to rise again. You then add more acid, aerate, and repeat this process until the TA is on target. See the sticky in the forum on how to lower TA for full instructions. It's pretty easy in a hot tub because to aerate just turn on all the jets and bubblers and open the venturis ( and turn on the blower if you have one). High TA and high pH tend to go hand in hand, BTW! That is normal.
    If the chlorine is low you need to add more. Period. End of story. It's really that simple! You want to be testing for Free Chlorine (good chlorine that is available to sanitize), btw. Total Chlorine the total of Free Chlorine and Combined Chloramines (spent or bad chlorine) so it is not really what you want to be testing for.
    As far as the calcium goes...if the tub is acrylic (most stand alone hot tubs are) you don't need to worry about low calcium. Ideally you want it around 130-150 ppm to minimize foaming but it really does not need to be any higher than that and many people run it lower. If the spa is plaster or aggregate then you do need to maintain enough calcium to maintain a proper calcium saturation index to protect the plaster finish.
    How are you testing the water. If you are using strips then your measurements are very possibly bogus. The fact that you stated the pH is over 8.5 leads me to believe you are using strips. Get a decent test kit. The one recommended is the Taylor K-2006. It will make maintaining your spa MUCH easer.
    Finally, you did not give us any test result numbers. A full set of test results (not done with strips) that include free chlorine, combined chlorine (or total chlorine so the combined chlorine can be calculated), pH, TA, CH, and CYA (cyanuric acid or stabilizer.....this is a needed test for any chlorine pool or spa!) would tell us better what might be going on in your water! Also, what is your primary chlorine source (dichlor, bleach or liquid chlorine, lithium hypochlorine, calcium hypochlorite) and how many gallons is the spa?
    11.75'x23.75' kidney 6.5K gal IG fiberglass pool/300 gal acrylic spillover spa combo; Aqualogic automation/SWCG; Pentair Clean and Clear 150 cart filter; 1.5 hp uprated 2 spd Pentair Whisperflo pump; PF:17
    Retired pool store and commercial pool maintenance guy.

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    Default Re: Low TC, high TA, High pH in hot tub-how to fix?

    Yes, BigDave, the fill water is from our well and is also TA. We are concerned about both. It just makes no sense to me that the (new) test strips would show almost zero TC, very high TA and very high pH....to me, this means we should add MORE calcium since it's zero, but that would, to my mind, make it only MORE alkaline...and would not lower either the TA or the pH. Even if we ignore the TC, how do we lower the pH and TA? (and thanks for taking the time to respond; much appreciated).

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    Default Re: Low TC, high TA, High pH in hot tub-how to fix?

    Thanks for your response, waterbear. Our hot tub is acrylic, about 3 years old; we use bromine floaters instead of chlorine. Yes, we are using strips...just bought some new AquaCheck strips, in fact from the spa place (different brand, we had been using HTH) - we will get the Taylor strips you recommend. The spa is about 300 gallons. Using our test strips we got the following readings, done 3X to make sure (including once on our well water, which we use to fill):
    Total hardness: zero (I assume this is TC, correct?)
    Total bromine: zero (because we haven't put any in yet; our last water test of the tub water before filling it was 'very high' (>20)
    Total alkalinity: high (240)
    pH: high (> 8.4)

    When the spa guys tested our old tubwater, he said it was basically battery acid because of the high bromine content - I wasn't getting why we would get such a high bromine content yet the pH is also way high, which to me indicates it's highly basic, not acidic. Your explanation of the high alkalinity leading to high pH makes sense. And you are the second person to say the very low calcium is nothing to worry about in a hot tub. So I guess we just need to lower the alkalinity at this point, which should lower the pH, and then add in however much bromine we need to bring it up to the ideal level of ~5 or so. I will consult the forum for how best to lower the TA. Thanks again for your quick response!

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    Default Re: Low TC, high TA, High pH in hot tub-how to fix?

    Maggie, you don't want to be testing with strips. Period! They are worthless! As far as it goes the HTH strips are among the better ones since they are rebranded Taylor strips but no strip can give you the precision and accuracy and ease of reading as a GOOD test kit and for bromine it is the K-2106! You will probably have to order it on the internet. Amato industries seems to have the best price for this kit. If you are running a bromine tub then you want to get a Taylor K-2106 test kit which will test for total bromine, pH with acid and base demand tests, Total Alkalinity and Calcium hardness. This si what you need to test in a bromine tub. Also I suspect that you need soem guidance in how to properly maintain your tub water so I am referring you to a thread on a different forum that has more info on hot tubs (and where I am one of the moderators) where you will find the info you are looking for!:
    Bromine for Beginners
    How to lower TA (along with an explanation of what TA is and why it causes pH to rise)

    Also, adding calcium has NO effect on the total alkalinity or pH of the water since it is added in the form of a neutral salt (calcium chloride).
    If your spa guy said your water was basically battery acid because of the bromine content then it's time to ditch the spa guy. He doesn't have a clue! Your pH is high BECAUSE your TA is high. Period. It is cause and effect! High TA and aeration = pH rise. Period. It's really not rocket science but many in the industry cannot grasp this simple fact.

    ====================================

    Also, the test for total chlorine and total bromine on the strips is the same test so if you have no bromine in the tub then the chlorine is going to register 0 also However, you really don't want to pay attention to any chlorine numbers since you are suing bromine. The tests are the same. The only difference is that to get a bromine reading the chloirne reading is doubled (actually multiplied by 2.25 but doubling is close enough for government work!)
    11.75'x23.75' kidney 6.5K gal IG fiberglass pool/300 gal acrylic spillover spa combo; Aqualogic automation/SWCG; Pentair Clean and Clear 150 cart filter; 1.5 hp uprated 2 spd Pentair Whisperflo pump; PF:17
    Retired pool store and commercial pool maintenance guy.

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    Default Re: Low TC, high TA, High pH in hot tub-how to fix?

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