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Thread: CYA into ammonia that quickly?

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    andyrob2215's Avatar
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    CYA into ammonia that quickly?

    Hey guys,

    I need some help. I went on a day trip and thought for sure I'd be okay with getting my FC up to 8 and it'd be at around 4 when I got back. Ad other times I have done this. Well, either the water temp being 92 or something else, I got home last night and it was a little cloudy with a slight green tint to it.

    I ran a full set of tests with CC at 1.5. So I began to SLAM. This morning there was no FC so it failed the OCLT.

    The thing I don't get is my CYA it extremely low. Possibly even 0 (I can still see the dot clearly all the way to the top.)

    2 weeks ago I had 35-40 CYA. I did the test 3 times just now. Is it possible it turned to ammonia that fast?

    The water is a bit clearer and no more green now btw.
    Here's my test results.

    FC~5
    PH 7.2 (adjusting now)
    TA 80
    CYA 0?

    I have to go to work in an hour so I need to figure something out quick. Thanks guys
    21'x52 AGP 11200 Gal
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    Texas Splash's Avatar
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    Re: CYA into ammonia that quickly?

    Normally we see the ammonia scenario come into play more at the beginning of the swimming season, or if someone allowed their FC to fall to zero. So that is odd. Something else we've seen several times this year are people complaining about CYA drops. Can't explain why. Bad batches of stabilizer? My CYA has dropped twice this season for no reason. So barring any testing errors, you may just have to overcome and adapt.
    You're about to leave to work, so you don't have time for this test, but the following is how we go about checking/resolving any suspected ammonia scenarios:
    1. Begin a SLAM and dose FC up to SLAM level. Do not add additional CYA at this point.
    2. Retest FC at 10-minute intervals.
    a. If FC loss is greater than 50%, add FC to bring back up to SLAM level and continue retesting FC @ 10-minute intervals.
    b. IF FC loss is 50% or less, add FC to bring back up to SLAM level. Go to Step 3.
    3. If CYA is below 30 ppm, add enough CYA to bring level up to 30 ppm.
    4. Continue SLAM as directed in the SLAM article until the SLAM Criteria of Done are met. Test as directed in the SLAM article - no longer need to test FC at 10 minute increments at this point.
    Good luck!
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    Re: CYA into ammonia that quickly?

    Awesome, thank you. I may not have been clear in my post. My FC DID drop to zero for an unknown amount of time.
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    Texas Splash's Avatar
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    Re: CYA into ammonia that quickly?

    Well, that may certainly be the culprit. Maybe that test process above will help get you on-track. Good luck!
    Pat (a.k.a. Texas Splash) ~ My Pool: Viking Fiberglass; 17,888 Gal; Waterway Supreme 2-sp/2-hp pump; Hayward Ctg filter; TF-100 w/ Speed Stir
    Vital Links: POOL SCHOOL, RECOMMENDED LEVELS, RECOMMENDED CHEMICALS, Poolmath Calculator, SLAM, Chlorine/CYA CHART.
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    andyrob2215's Avatar
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    Re: CYA into ammonia that quickly?

    Thank you.

    I mainly wanted to find out if indeed I had no CYA and I'd hate to add more to find out it was there all along. This test will explain. Thanks again
    21'x52 AGP 11200 Gal
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    Re: CYA into ammonia that quickly?

    My cya drops about 7-8 ppm per month. I've only ever used trichlor tabs to adjust cya. But never a major drop like yours.
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    Re: CYA into ammonia that quickly?

    See It Can Happen to Anyone - Zero Chlorine, CYA-->Ammonia. As summarized in this post in that thread, the FC probably got to zero and the bacterial conversion of CYA into ammonia took place over just 6 days and I suspect was mostly over around 3 or 4 days. So yes, it can take place rather quickly when the pool is rich in nutrients (my phosphate level was 3000+ ppb at the time). Fortunately I caught the conversion before it completed otherwise it would have taken even more chlorine to get back to normal.

    In your case you might be lucky that the conversion went to nitrogen gas or nitrates so that you won't have a huge chlorine demand. The fact that you are measuring FC that appears to be holding is a good sign.
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    Re: CYA into ammonia that quickly?

    Before I left for work, an hour after posting and adding chlorine. I added enough to get to SLAM level it read ~7ppm so it is "holding" but still going down fast
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    Re: CYA into ammonia that quickly?

    If you haven't added any CYA yet then this loss could be from sunlight. You will lose about half the FC every hour in direct noontime sun with no CYA. It's if you lose almost all of it in minutes that you have ammonia in the water since that very quickly combines with chlorine and will measure as CC. It sounds like you don't have any ammonia left but may now have monochloramine to get rid of (if you measure CC) or partially degraded CYA to get rid of. Follow the procedure Texas_Splash gave you.
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    Re: CYA into ammonia that quickly?

    This morning I tested 1.5 CC. I now have 0-.5 CC with a FC of 16.
    It passed the test above. So I will add CYA in the morning after I go get some from the store. The gradations on the CYA tube aren't equal in measurements so what would the top of the tube be? 15? That's where it begins to be hard to see the dot. So not ALL the stabilizer was lost. I will measure FC in the morning to see if it passes the OCLT as CC is already below .5.

    Also, PH tends to do funny things when chemistry is played with, yes? I have always had a very steady PH but it is staying very low after adding enough borax to raise it up. Here's my numbers again:

    FC: 16
    CC: 0-.5
    PH: 7.2
    TA: 95
    CYA: ~15

    Thanks for the help.
    21'x52 AGP 11200 Gal
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    Re: CYA into ammonia that quickly?

    The CYA tube in the TF-100 only goes to 20 ppm so if the dot doesn't disappear at that point it's just <= 20 ppm. If the water in the tube is very clear then you probably have no CYA. If the dot went away with the tube filled to the top, then yes figure you've got a little less than 20 ppm and add CYA accordingly. You should round up with your guess so that you don't overdose with CYA. You can always retest after adding the first dose of CYA and add more if necessary later.
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    Re: CYA into ammonia that quickly?

    Okay, thank you.

    One last question. With CYA <20, is the OCLT still valid as far as 1 ppm or less loss overnight? I assume so since CYA protects against sunlight and not overnight. When I woke up this morning I had lost 6ppm from 16. So it is now 10.
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    Re: CYA into ammonia that quickly?

    No, an OCLT will be higher than normal at a low CYA because the FC/CYA ratio will usually be too high. The chlorine loss rate will be roughly proportional to that ratio. So even a "normal" loss rate will be higher and you might exceed the 1 ppm OCLT criteria. So I wouldn't bother with an OCLT when the CYA is very low (especially below 20).

    For example, if you had no CYA at all, then the 16 ppm FC would be nearly 27 times higher in active chlorine than a regular SLAM level (which at a 40% FC/CYA ratio is roughly equivalent to 0.6 ppm FC with no CYA). So your 6 ppm FC loss could be normal if there were no CYA in the water. Even 16 ppm FC with 20 ppm CYA would be equivalent to 2.5 ppm FC with no CYA so over 4 times a regular SLAM level. At such high active chlorine levels, chlorine can outgas from the water to cause a drop. In fact, keeping a bucket of water uncovered for a day or two (even not exposed to sunlight) is one way it can be largely dechlorinated -- I used to do that for tap water before putting it into fish tanks in high school many years ago.
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    Re: CYA into ammonia that quickly?

    Quote Originally Posted by chem geek View Post
    No, an OCLT will be higher than normal at a low CYA because the FC/CYA ratio will usually be too high. The chlorine loss rate will be roughly proportional to that ratio. So even a "normal" loss rate will be higher and you might exceed the 1 ppm OCLT criteria. So I wouldn't bother with an OCLT when the CYA is very low (especially below 20).

    For example, if you had no CYA at all, then the 16 ppm FC would be nearly 27 times higher in active chlorine than a regular SLAM level (which at a 40% FC/CYA ratio is roughly equivalent to 0.6 ppm FC with no CYA). So your 6 ppm FC loss could be normal if there were no CYA in the water. Even 16 ppm FC with 20 ppm CYA would be equivalent to 2.5 ppm FC with no CYA so over 4 times a regular SLAM level. At such high active chlorine levels, chlorine can outgas from the water to cause a drop. In fact, keeping a bucket of water uncovered for a day or two (even not exposed to sunlight) is one way it can be largely dechlorinated -- I used to do that for tap water before putting it into fish tanks in high school many years ago.
    Ahh I see. That makes it much more clear to me. Thanks for clearing that up.

    Well, I added enough CYA to get up to 40, my water is crystal clear again, and FC is "holding" given the circumstances. I think I'm in the clear. I'll test in a few days for the CYA. And keep a close eye on other levels. PH is still hovering around 7.2 which is okay I suppose but given the "high" FC and newly added CYA, it may not be accurate. So I think I'll wait to adjust that.
    21'x52 AGP 11200 Gal
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