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Thread: TA Test showing only 30ppm?

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    TA Test showing only 30ppm?

    I just did my OTO test for TA (Total Alkalinity) and I added 3 #3 drops to get it to light yellow. The fourth did nothing more, so I guess the result is 3.

    That means 3 x 10ppm = 30ppm according to the chart and instructions.

    But does this mean my TA is LOW or HIGH??? I mean, do I have 30ppm and I need ~100ppm, so add 70ppm?!?!? OR does this mean add 30ppm to get to 100?!?!??!

    I am thinking it means my TA is only 30, as this is a new pool (3 weeks old) so that does make some sense that is has not built up TA yet.


    Here are the other results I got:

    Residual Chlorine: 2.25
    pH: 7.4, which is basically fine, I might add a dash of borax though
    TA: 30ppm I guess

    So I figured my TA is just low and I read to fix TA before messing with pH, as it's a waste of time. So I put in 6lbs of Baking Soda (100% sod bica), 3lbs twice 8 hours apart. I tested before the 2nd 3lbs and it had no impact on the OTO test (I probably need a more accurate test).

    I will retest later tonight and publish the results but any insight into this is much appreciated.

    Thanks!

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    JasonLion's Avatar
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    Welcome to TFP!

    The OTO test, various shades of yellow compared to a color standard, shows the total chlorine level, TC, not total alkalinity, TA. This test is normally done by adding five drops of reagent and then comparing the sample to a color standard (which will list the TC level that goes with each color).

    The standard TA drop test first turns the sample green and you then add drops till the sample turns red. In that test, three drops means TA is 30. For most pools the ideal TA is around 70 to 90, but it depends on what form of chlorine you are using and what the pool surface is.

    If your pool is plaster/gunite/pebble/quartz/diamond brite/or tile you should keep in mind that the PH & TA levels will go up as the plaster/grout cures.
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    Thanks for the reply Jason!!

    My OTO kit has a TC test like you said, but it also has the TA test, I was referring to. My TA test turns it blue and it goes to yellow. It says in the book some go blue->yellow some go green->red. It depends on the model apparently.

    In any event, I need to bump my TA it would seem (about 70ppm needed) and after 3 weeks, hasn't the plaster cured already??

    So I should add a bunch of baking soda (as per your pool calc), right?

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    Alright, just a naming issue. Only the chlorine test is actually called an OTO test. The OTO test is often packaged together with other tests.

    Right, sometimes the TA test goes blue/yellow instead of green/red.

    The majority of the plaster curing will happen in the first three or four weeks. After that, it will continue curing much more slowly for up to a year.

    Since the plaster isn't brand new you might as well go ahead and adjust the TA up to around 60 or 70. I am suggesting the low end of the range because the plaster curing will still raise it a little more.

    PH between 7.4 and 7.6 is ideal. There isn't any reason to try for exactly 7.5. Adding baking soda will raise the PH a little and over time I would expect the PH to drift up slowly, so no reason to add any borax right now.
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    Roger that..

    And just to confirm, even if the pool calculator says something like toss in 139oz (9lbs) of baking soda, I should do it, right?!?!?

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    Yes, 9 lbs isn't really that much, my pool needed over 20 lbs at startup. It is almost always a good idea to not add all of it at once, to kind of sneak up on the reading you want. I would do perhaps 3/4 of that and see where that gets you, and then adjust from there.
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    Well, I did 2/3, 6lbs instead of 9lbs.. It was all I had - need to go back to the store..

    This morning my TA took 5 drops (vs. before it was 3) to make the color change as per the instructions.

    So that means my TA is now 5 x 10ppm = 50ppm!!

    WOOHOO, IT IS WORKING!! Only another 50ppm to go!!

    So if 6lbs of Baking Soda gave me 20ppm extra, then it is less that I had hoped, but at least it is going in the right direction.. Now I just need to hit up the store for some more Baking Soda...

    Another question: How quickly/slowly does TA move once it is at, say 100ppm?? I'm guessing not near as frequently as CL and pH levels, right??


    I just found this on armhammer.com:

    But it should be noted that trichloroisocyanurate tends to use up the pool
    alkalinity more quickly than other chlorinating agents. As a rule of thumb, the
    alkalinity lost can be replaced by adding ARM & HAMMER® Baking Soda at the
    rate of 1.5 kg (1.5 pounds) for each kg (pound) of trichloroisocyanurate used.
    It is preferable to keep the alkalinity in the 110 –150 ppm range when this
    chlorinating agent is used.
    So I guess if you're using Trichlor, like I am primarily, then I can maintain my TA level by matching my Trichlor with more Baking Soda (in weight).. I guess this makes it more expen$ive, but having ~100ppm TA levels will probably make my pool (and pH) maintenance a whole lot easier, right???

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    IP,


    reading your last post, I'm gonna chime in with something that may be obvious to you so don't be miffed by my good intentions........Most of your test numbers...pH, CH, CYA, Alk will remain somewhat constant unless you do something to change them. That's a broad statement and not perfectly true but I say it to make a point.

    Chlorine, on the other hand, is a consumable and will CONSTANTLY need to be replenished in your pool. 2ppm daily is a fairly average chlorine loss,,,maybe a little higher in the Summer.
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    Actually, that is the kind of reply I was looking/hoping for!! Thanks!! I think it is all beginning to make sense now, and I'm glad I am fixing TA before messing with pH.. BTW, my pH is perfect today all by itself.. but I think another couple days of Baking Soda could change that. Ditto with CYA and CL - no point in putting in high CL if my CYA isn't high enough (40ish) to protect it.. Plus it's not quite swim season, so I still have time to make this all perfect before I gotta swim in it..

    Right now I'm going day by day, but once this is all up and stablizied, I will probably focus on testin CL and pH daily and then CYA and TA weekly..

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    CYA of around 40 is perfect. If you are using trichlor your CYA will possibly get too high after a while and you wlll need to do the 'drain and refill' dance! If you have a cartridge filter or a non backwash DE filter this will happen a lot sooner than you think!

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    Another update...

    I now have 6lbs + another 8 today, and I'm at 80ppm this afternoon. It may change some more over the next few hours, so I will hold off until tomorrow to re-test and hopefully finish up the last 20ppm to reach my goal of 100ppm.

    I need to add some Acid though because of all of this, so in goes ~20 ounces..

    After my TA gets to 100, I want to work on getting pH perfect and then it SHOULD STAY, RIGHT??

    Also next will be CL.. I have like 3.2ppm right now which is way too much, esp for the off-season.. Right? So I want to get it down to like 1.5 or even 1 for now.. make sense? Anyone know which trichlor setting on my Raibow I should use? The canister holds 10 3" pucks.. It's 1/2 full now I think. I am going to use Trichlor for a while to get my CYA up and then switch to Bleach, sound good??

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    I need to add some Acid though because of all of this, so in goes ~20 ounces..
    Why? Did you test pH? It typically moves little when adding baking soda....particularly if you're chlorinating with pucks which are highly acidic.
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    Yes, my pH was showing 8.2 this morning. But also poolcalculator.com says "Adding baking soda will also raise your PH." so.......

    Also, I guess it is just still quite volatile, as the plaster finishes curing especially, and because the TA is/was still so low.. Hopefully now that the TA is up, the pH will settle down a bit..

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    IP,

    That's a very big jump from 7.4 on Sunday to 8.2 this morning. Baking soda won't do that. Is this a new pool? Let us know the gallonage and type of pool (AG or IG, vinyl or gunite, etc)

    After my TA gets to 100, I want to work on getting pH perfect and then it SHOULD STAY, RIGHT??
    Well, probably not perfect....there's lots of factors at work. The pucks (which you should stop using very soon....read waterbear's post) are very acidic (about 4.9, I think) and will lower pH. That said, each pool is a little different and your pH may drift up or down over the summer requiring you to adjust 2-3 times or so

    Also next will be CL.. I have like 3.2ppm right now which is way too much, esp for the off-season.. Right? So I want to get it down to like 1.5 or even 1 for now.. make sense?
    Actually, I think I'd leave it right there. The appropriate Cl level is dependant on your CYA level. Find Chemgeek's CYA/chlorine chart (I think it's in the stickies) and you'll find your just about correct............you'll actually need to run it higher if you let your CYA increase.

    Keep asking questions. This is just a little confusing at first, then it becomes second nature.
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    Yes, it is a big jump, but my plaster is less than 4 weeks old, and I just added some tap water and also according to the poolcalculator.com, Baking Soda *DOES* raise the pH slightly.

    Here's some specs on my pool, btw...

    I've done a LOT of calculations on the amount of water, and I usually come up around 9500 gallons of water incl. 10x32 freeform pool that goes from 3-6 (avg. 4.5) and 7' round Spa with spillway, including a huge 4 cartridge filter which holds like 10 gallons, and a scupper which holds 2-3, plus all the piping runs, many of which are 20-40 feet long.

    I just realized the spillway aerates the water, right? So that might be affecting pH.. I also have a scupper. These are on about 10 hours a day right now.. But I can't stand the idea of sitting poolside without them on!! TOO QUIET!! And I'm out there, or plan to be, A LOT all day, as I work from home (this summer it will be "work from pool")...

    In any event, I put in some acid earlier as I stated (1:30 today) and now I just re-tested:

    CL: 3ppm residual
    pH: 7.7
    TA: 90ppm!!!!

    I'll add a few more drops of acid to get it down to 7.5, but I'm happy now because my TA is finally up to 90.. I'll add another 10ppm to make it an even 100 and then I should be done with that..

    I guess next on the list will be measuring CYA once I get my new test kit, TF-100!!!!, and then switching to Bleach after CYA hits ~40, and also look into doing the Borate thing a few weeks after that...

    Anything else?? I guess the rest I'll play by ear.. Like CH, I am waiting on my new test kit for, but hopefully that is not a problem yet..

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    Hey, IP,

    Thanks, that gives us a much better picture. My guess is that with a new plaster pool AND the aeration those two factors account for most of your pH rise. The plaster will subside as it cures but the aeration will always have a tendency to raise pH. Maybe not much but as long as you test, you'll get a feel for it quickly.

    Your Cl will continue to deplete slowly so remember to check it often and add as needed. Sounds like your getting a good handle on most of this stuff.

    Remember that pH and Alk are co-dependant and are affected by many factors so don't expect them to be perfectly stable all summer.
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    I am wondering if there is something, easy (read: not acid), I can do to automagically make my pH trickle down lower, to counteract the aeration and keep it mostly level in the 7.5 area... ???

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    Quote Originally Posted by IPvFletch
    Yes, it is a big jump, but my plaster is less than 4 weeks old, and I just added some tap water and also according to the poolcalculator.com, Baking Soda *DOES* raise the pH slightly.
    New plaster will cure and this causes the pH to rise and there is nothing you can do about that -- even having a lower TA to reduce carbon dioxide outgassing won't help because the amount of pH rise from the curing is typically far higher than any outgassing effect. So having the TA be closer to normal (80-100) doesn't change the amount of acid you need to add, but it does slow the rate of pH rise (from the curing, though somewhat increases the rate from the outgassing) so you may not need to add the acid as frequently. So unfortunately there is nothing you can do except periodically add acid. The good news is that this pH rise from curing will decline in intensity over time -- the first month is worst. After 3 months you should notice it being less, but it will still have some effect for 6 months or even 1 year. Just hang in there -- pool owner patience (POP) is what is required.

    The curing of plaster adds calcium hydroxide to the water. As an example, if the curing adds 10 ppm to Calcium Hardness (CH), then at a TA of 100 and starting pH of 7.5 it will make the pH rise to 8.34 and require 25 fluid ounces of Muriatic Acid in 10,000 gallons to lower the pH back to 7.5.

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    This morning's pH was 7.8 and TA was 85ppm, so the Baking Soda is doing its job... I put a few more oz of Baking Soda in and also tossed in a bit more acid. Hopefully it will be 100ppm/7.5 by the end of today. Wheee!!!

    I understand the year-long curing process and also aeration.. But next year, my pH still rise due to aeration, right? Maybe not as quickly as plaster curing, but still some. So I am thinking I may keep my pH on the low side, say 7.4, and let it slowly aerate up to 7.7 before adding a few drops of acid.. Does that make sense??

    Does Trichlor also increase the pH? What about Liquid Chlorine?

  20. Back To Top    #20
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    Trichlor lowers PH over time while liquid chlorine (bleach) leave PH more or less the same.
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