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Thread: Thought I knew what I was doing... but I guess not

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    Thought I knew what I was doing... but I guess not

    I am making myself crazy trying to understand a puzzling change in test results. I apologize NOW for the length this post will surely stretch to.

    On 6/10, I discovered a full-blown algae bloom (especially discouraging because I cased it with an exceptionally STUPID mistake). At that point, except for FC & CC, my numbers were solid:

    pH - 7.3 (low - but I had just added acid to lower TA, and was aerating to raise)
    FC - .5
    CC - 1.0
    TA - 90
    CYA - 70 (tested five days prior, and I had added a pound to try sneaking up to 90)

    So I started the shock process. SWG was turned off, and I began with 12 bottles of 6% bleach targeting a FC of around 30. Then I moved to gallon bottles of 12.5%. Everything I added seemed to be consumed almost immediately. I won't bore you with all the details, but in summary, it was a real struggle to keep FC near 30. It occasionally got as low as 22, but was always at least in the high 20's, and once as high as 44 (at 11 pm on 6/16).

    I have gone through a staggering (to me) amount of 12.5% bleach in the last 10 days (~ 40 gallons 12.5% + 12 96oz bottles of 6% -- in an 11K gallon pool). Throughout this time, I was testing only FC and CC using the FAS-DPD method (understanding pH test is inaccruate at FC > 10). Water color and clarity was improving daily, but v-e-r-y s-l-o-w-l-y. Because I had been pouring SO much bleach in for over a week, I *assumed* the lack of complete clarity could be associated with some other parameter. Overnight tests had a FC drop of 2.0 & CC of .5. No... I didn't go all the way to an overnight FC drop of 1.0... but I figured I was in good shape with CC consistently at .5. Again, I had added a LOT of bleach to this pool. I wanted to let the FC drop so I could run a complete test again.

    Yesterday morning, the water contained FC = 14.0, CC of .5. I did not add chlorine during the day. By 10:30 pm, I had FC of zero. I added three gallons of 12.5% bleach (which should be approx 35 ppm), and 30 minutes later, measured FC of 15, CC of .5.

    This morning, I ran complete numbers, and received... Odd results:
    FC - 13.0
    CC - 1.0
    pH - 8.0 (accurate with this FC level???)
    TA - 170 (How could it be nearly double???)
    CYA - ZERO

    The water is still cloudy white, but I can see the bottom of the deep part (around 5.5 feet down)

    So... Now what? I suspect I need to shock again, but was amazed to see CYA of zero. I suppose I must have screwed up that test, because I surely did not replace 11,000 gallons of water. But is there some environmental factor that could cause this result?

    Perhaps the solution is to bring in a bulldozer and a big pile of topsoil... {sigh}
    Greg R.

    12,000 gallon fiberglass in-ground, Aqua-Rite SWG, 1 HP single speed Hayward Super Pump, Hayward 200# top valve sand filter, 150K BTU Natural Gas heater, automatic cover, Blue Diamond robot, and lots of noodles.

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    JasonLion's Avatar
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    Re: Thought I knew what I was doing... but I guess not

    It is possible, though extremely rare, for CYA to fall dramatically while you have algae. How are you testing your CYA level (what kind of test kit and how old)?
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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    Re: Thought I knew what I was doing... but I guess not

    I'm using the graduated flask and mixing bottle I got with my TF-1000. The reagent is a Taylor bottle I bought locally (R-0013 I think?) within the last 12 months when the supply that came with my kit ran out. Same stuff that came with my TF-1000.

    I need to retest... maybe I can run home at lunchtime. Surely I screwed something up. I've dealt easily with algae blooms using BBB in the past. This one has been a real [Edit: Language. Butterfly] .
    Greg R.

    12,000 gallon fiberglass in-ground, Aqua-Rite SWG, 1 HP single speed Hayward Super Pump, Hayward 200# top valve sand filter, 150K BTU Natural Gas heater, automatic cover, Blue Diamond robot, and lots of noodles.

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    Re: Thought I knew what I was doing... but I guess not

    What was your last CYA reading, prior to it being zero? Also, do you have an autofill? I ask that because sometimes pools that leak have the leak masked by an autofill. One way to lose your CYA is through a leak.

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    Re: Thought I knew what I was doing... but I guess not

    My last CYA reading was 70ppm on 6/5. I added about 20 ounces of dry stabilizer in a sock through the skimmer the next day trying to elevate closer to 90 as I have a SWG.

    No autofill, but I did add some water once during the shock process. I had backwashed the filter a couple of times, and the level dropped a bit lower than I like. I don't know what flow rate I have from my garden hose, but the amount of fresh water I added might have been 200 - 300 gallons, tops.
    Greg R.

    12,000 gallon fiberglass in-ground, Aqua-Rite SWG, 1 HP single speed Hayward Super Pump, Hayward 200# top valve sand filter, 150K BTU Natural Gas heater, automatic cover, Blue Diamond robot, and lots of noodles.

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    Mod Squad zea3's Avatar
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    Re: Thought I knew what I was doing... but I guess not

    You said at the begining of the post the algae was caused by a mistake, what was the mistake?

    After you retest the CYA, if it is truly 0, test the pool for ammonia. Have you recently had any fertilizer near the pool?
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    Re: Thought I knew what I was doing... but I guess not

    I'd go to an aquarium store and get your water tested for Ammonia.

    Ammonia will cause your FC to be consumed like nobody's business, and, I have seen theories where CYA can become converted to amonia ... or Ammonia can cause the conversion... I don't recall exactly.

    Regardless... the check for ammonia can reveal a part of the puzzle, not that it will necessarily change your game plan much.

    Another suggestion: Balance a bucket of your pool water. This will do nothing except show you GENERALLY what needs to be done, and give you sanity that there is a light at the end of the tunnel. But do not try to do any math to extrapulate what quantities of chemicals you will need to add to your pool that were required to balance your bucket. The economies of scale simply do not convert really well.

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    Re: Thought I knew what I was doing... but I guess not

    The reagent is a Taylor bottle I bought locally (R-0013 I think?) within the last 12 months when the supply that came with my kit ran out. Same stuff that came with my TF-1000.
    Have you done a test with that reagent (and R-0013 is correct) that has given you a valid result?

    If you had a result of 70 and the ONLY thing that changed was the reagent bottle, that's the first thing I would check....simply by getting some more reagent.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
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    Re: Thought I knew what I was doing... but I guess not

    Firstly, thanks to all for weighing in.

    Ah... the mistake. Truly boneheaded. All my fault. I was having problems with cloudy water early on, despite good healthy (I thought) numbers. pH (7.4), FC (4.5), TA (90), CYA (70)... all were right where I wanted them - or nearly so. So I changed out the sand in my filter -- and the water became perfect. Absolutely crystal clear. Up to then, I had been filtering 24/7. So once the water cleared, I knocked the timer back to run 12 hours a day. Unfortunately, I forgot to adjust the SWG percentage. With half the filter time, I should have doubled the percent of 'ON' time. I didn't. The SWG couldn't keep up, and three days later the pool was green. {sigh}.

    The bottle of reagent I used for the test was the same one I used back on the 5th to get a reading of 70ppm. But it IS a bottle I purchased last year...

    I have not fertilized anything in the yard lately, so I'm not sure how ammonia would be introduced into the water. But it's worth a try. Not sure if we have any true aquarium stores in town, but I'll definitely check for someone who can test that for me.

    I didn't get a chance to re-test at lunchtime as I'd hoped. So it will be the first thing I do when I get home from work. Maybe I'll be able to swing by the pool store to pick up fresh bottle.
    Greg R.

    12,000 gallon fiberglass in-ground, Aqua-Rite SWG, 1 HP single speed Hayward Super Pump, Hayward 200# top valve sand filter, 150K BTU Natural Gas heater, automatic cover, Blue Diamond robot, and lots of noodles.

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    JasonLion's Avatar
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    Re: Thought I knew what I was doing... but I guess not

    When CYA vanishes, it is often because it has broken down into ammonia, which is where the ammonia would have come from.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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    Re: Thought I knew what I was doing... but I guess not

    So assuming my CYA again tests out to zero, I should start with adding stabilizer?

    And bleach?

    Do I also start adding acid to bring TA and pH back down? or should I wait until the water clears more?

    I am nervous with trying to adjust so many parameters at once, and am not quite sure where to begin.
    Greg R.

    12,000 gallon fiberglass in-ground, Aqua-Rite SWG, 1 HP single speed Hayward Super Pump, Hayward 200# top valve sand filter, 150K BTU Natural Gas heater, automatic cover, Blue Diamond robot, and lots of noodles.

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    JasonLion's Avatar
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    Re: Thought I knew what I was doing... but I guess not

    As long as the FC level is below 10, lower the PH to 7.2 before continuing.

    Then you want to continue shocking the pool and start adding CYA at the same time.

    Don't worry about TA until you are done shocking.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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    Re: Thought I knew what I was doing... but I guess not

    Thanks for the guidance Jason.

    As of 6:00 pm yesterday, I got FC = 9.5, CC = .5, pH = 7.9ish (between 7.8 & 8.0 on the comparator). CYA again tested at zero with a new bottle of reagent. I added acid in small doses, and by 9:45 the pH was at 7.2. I also placed a nylon stocking with 4 lbs of CYA in the skimmer -- which should yield approximately 44 ppm.

    At 7:15 this morning, I had FC = 8.0, CC = .5, pH at 7.2. I added 12.5% bleach sufficient to raise FC to approximately 25 ppm and thoroughly brushed the pool. Unfortunately, I won't be able to test again until after work.

    Today's questions:
    1) Why in the world will my CYA suddenly break down into amonia? Is this common? Was it related to the algae bloom? (is this question better posted in "The Deep End"?)
    2) Since CYA can't be measured until a week after application, how do I know if the new stuff I'm adding isn't breaking down as well?
    3) Since my FC only dropped 1.5 ppm overnight, can I assume my ammonia has or is nearly dissapated?
    4) When shocking I always keep the automatic cover closed, thinking this helps minimize FC breakdown by limiting sunlight on the pool. However, will this keep things like ammonia or CO2 from outgassing?
    Greg R.

    12,000 gallon fiberglass in-ground, Aqua-Rite SWG, 1 HP single speed Hayward Super Pump, Hayward 200# top valve sand filter, 150K BTU Natural Gas heater, automatic cover, Blue Diamond robot, and lots of noodles.

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    Re: Thought I knew what I was doing... but I guess not

    Greg,

    1. It is related to an algae bloom but usually over a long period of time in the off-season. It is not common but not unheard of. WHY? Who knows. That seems to be what happened and you seem to need some more cYA

    2. The new stuff will work. Besides, you have no choice but to replenish.

    3. Yes

    4. Open that cover! Aside from some chlorine loss and a little dirt getting in, sunlight can be good for your pool....it'll help burn off CC's during the shock process.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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