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Thread: CYA dropped to below 30

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    CYA dropped to below 30

    This is my first summer with a pool and the TFP method has been wonderful - giving me a beautifully clear pool all summer. At the beginning of the summer, I had a high CYA level and had to replace water to bring it down to 40. I checked my CYA level for the first time in a little over a month today and it is below 30. I completely filled the tube and could still see the black dot. I am out of R-0013 reagent and just reordered a 16oz bottle, so I'll have to wait about a week or so before I can check it again.

    First, I'm not real sure how this could have happened since the only way to lower CYA is to replace water. I do get a lot of rain in my area - could that explain it? It's also possible I simply messed up the test, but again I can't confirm it at the moment.

    Second, should I even bother raising CYA? I've been maintaining my FC level at 5 ppm, but I only lose 1-2 ppm a day. I very rarely lose more than 2 ppm in a day. If that rate of decline stays the same, do you think it's even worth bothering raising CYA?

    I do have some 1-inch trichlor tabs left over from the previous owner I can put in the skimmer basket, so it will be easy enough to raise the CYA.

    Thanks for your help!

    EDIT:

    I thought I should add my full test results:

    FC - 3.5 (just raised to 5)
    CC - 0
    PH - 7.8
    TA - 70
    CH - 120
    CYA - <30

    I may test CH again in the morning as well. Borjis's comment below helped me realize that if CYA has fallen I should expect to see CH fall too. This test would indicate it hadn't changed, but I had difficulty with that test today as the sample turned from a very faint red to a very faint blue. It was so faint I may have misinterpreted when it turned from red to clear to blue.
    Last edited by bjbarlowe; 07-08-2016 at 07:31 PM. Reason: Added test results
    12250 gallons | IG | Vinyl liner | Sand Filter | Emerson 1081 Pump EUST1102 | Hayward Pro Series High Rate Sand Filter Model #S166T | Pool <10 yrs. old | Taylor K-2006 test kit | SharkVac automatic pool cleaner

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    Re: CYA dropped to below 30

    I would wait until you get the reagent before adding anything. In the meantime, you probably want to maintain your chlorine level as if you were still at 40, just in case.
    50,000 gallon plaster in-ground salt pool with two 60 sq ft DE filters, two Intellichlor IC60 SWGs, two Intelliflo VS pumps, two Whisperflo pumps, two Pentair 400K BTU NG heaters, PCC2000 in-floor cleaning system...two everything.

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    Re: CYA dropped to below 30

    Yes, thanks. I'll keep my chlorine level at the target 5ppm for 40 CYA until I can retest.
    12250 gallons | IG | Vinyl liner | Sand Filter | Emerson 1081 Pump EUST1102 | Hayward Pro Series High Rate Sand Filter Model #S166T | Pool <10 yrs. old | Taylor K-2006 test kit | SharkVac automatic pool cleaner

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    Re: CYA dropped to below 30

    I've just had the same thing happen. CYA is 20 and was 50, 2 months ago.

    I have done no drains or backwashes, it has not rained....will start my own thread after
    I test CH, if it is the same as it was then I have a magic pool.
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    Re: CYA dropped to below 30

    Same here, mine was at 50 two months ago and I haven't checked it, decided to check it today and it's below 20. Weird. I've been having to add more chlorine lately so that's why I suppose. It's so hot here, the pool water has been at 94 the past couple of days. So refreshing!
    AGP 33' x 54" Lomart Verona, Approx. 27,300 gallons, Pentair cartridge filter/pump 2-speed, 1.5 hp, Dolphin Escape robotic cleaner.

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    Re: CYA dropped to below 30

    Keep in mind that the CYA test is very dependent on the proper lighting while doing the test. Done in different lighting will produce different results. It should be done in full sun with your back to the sun. More here. Pool School - CYA
    18*36*23 true "L" vinyl IG 29,000 gallons. SWG. TF-100 test kit.
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    Re: CYA dropped to below 30

    I was going to start another thread on CYA going down as mine has as well to even a larger extent but I've been trying to research all the threads out there first to not be redundant. It does seem to go down despite no obvious reason like draining or excessive rain.
    15000 gallon in-ground concrete pool, plaster finish. 1hp Sta-Rite P6RA6E-205L pump, Sta-Rite 2 cartridge filter, Rheem electric heat pump, no spa or water features.

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    Re: CYA dropped to below 30

    After reading some other threads on this (which I should have done before posting), it looks like CYA can degrade faster than normal if 1) Your FC level drops to 0, or 2) your FC level gets to high levels relative to CYA (at shock level) for a considerable period. Another factor that leads to faster CYA degredation is higher water temperatures. My FC has not gone to zero, but I have taken two weekend trips where I brought the FC level to or above shock level so I wouldn't drop below the minimum while I was gone. That and heavy rain plus a couple backwashes may have caused this.

    I'll retest when I get more reagent next week and just switch to my trichlor tabs for a little while and/or add liquid stabilizer if I need to.
    12250 gallons | IG | Vinyl liner | Sand Filter | Emerson 1081 Pump EUST1102 | Hayward Pro Series High Rate Sand Filter Model #S166T | Pool <10 yrs. old | Taylor K-2006 test kit | SharkVac automatic pool cleaner

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    Re: CYA dropped to below 30

    Quote Originally Posted by bjbarlowe View Post
    After reading some other threads on this (which I should have done before posting), it looks like CYA can degrade faster than normal if 1) Your FC level drops to 0, or 2) your FC level gets to high levels relative to CYA (at shock level) for a considerable period. Another factor that leads to faster CYA degredation is higher water temperatures. My FC has not gone to zero, but I have taken two weekend trips where I brought the FC level to or above shock level so I wouldn't drop below the minimum while I was gone. That and heavy rain plus a couple backwashes may have caused this.

    I'll retest when I get more reagent next week and just switch to my trichlor tabs for a little while and/or add liquid stabilizer if I need to.

    Maybe thats why my CYA levels have dropped as well. Hmmm interesting..
    IG Pebble sheen blue surf approx. 14k gallon, beach entry, 7' spa, 3.5 ton jumping rock/waterfall, Pentair 2hp whisper flo, booster pump, 520 cartridge filter, Stenner Econ T, 400k master temp heater, easy touch controls,TF-100 w/speedstir

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    Re: CYA dropped to below 30

    I was wondering if you lose CYA to evaporation. Mine was 50 and the last time I checked it a week ago, it was 40. I lose around 2-3" of water a week to evaporation right now. So does anyone know if the CYA goes with the water when evaporation happens?
    26k Gal IG vinyl, Hayward Super 1HP, Hayward Pro Series S244T Sand Filter, TFTestkits TF-100 w/ Speedstir
    Links: TFPC for Beginners / ABCs of Pool Water Chemistry / GETTING STARTED / PoolMath / SLAM / TFTestkits / Chlorine/CYA Chart

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    Re: CYA dropped to below 30

    Quote Originally Posted by JesseSchmidt View Post
    I was wondering if you lose CYA to evaporation. Mine was 50 and the last time I checked it a week ago, it was 40. I lose around 2-3" of water a week to evaporation right now. So does anyone know if the CYA goes with the water when evaporation happens?
    As far as I know, you can't lose CYA due to evaporation. From what I've read here and elsewhere, the only way CYA could lower is if you replace water (not by evaporation) or if the FC level gets low enough that bacteria can form, which naturally convert CYA to ammonia. Also, apparently very high FC levels can break down CYA.
    12250 gallons | IG | Vinyl liner | Sand Filter | Emerson 1081 Pump EUST1102 | Hayward Pro Series High Rate Sand Filter Model #S166T | Pool <10 yrs. old | Taylor K-2006 test kit | SharkVac automatic pool cleaner

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    Re: CYA dropped to below 30

    Quote Originally Posted by JesseSchmidt View Post
    I was wondering if you lose CYA to evaporation. Mine was 50 and the last time I checked it a week ago, it was 40. I lose around 2-3" of water a week to evaporation right now. So does anyone know if the CYA goes with the water when evaporation happens?
    That sounds like a leak. If that is the case and you are refilling with tap water (CYA of 0) that would explain your slow loss.
    32K gallon Plaster - 1hp Hayward 2 speed Super Pump - Hayward S200 Sand Filter - TF100XL
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    Re: CYA dropped to below 30

    Quote Originally Posted by NSBFAN View Post
    I was going to start another thread on CYA going down as mine has as well to even a larger extent but I've been trying to research all the threads out there first to not be redundant. It does seem to go down despite no obvious reason like draining or excessive rain.
    Mine has gone down too. The only thing we've had to do is to add water since we haven't really had any rain here lately.
    Pool completed 3/21/2016
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    Re: CYA dropped to below 30

    Splash out also contributes to lower CYA
    14.3k, 3 1/2-5 1/2, IG, Pebble Wet Edge Northshore Tahoe, Jandy 4 cartridge, Jandy 2hp variable, Pentair 320 inline chlorinator fed by a Stenner, Polaris 280, K-2006 test kit, Built 9/13
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    Re: CYA dropped to below 30

    I have had no splash out, I'm the owner/lifeguard when guests come over and not witnessed any.
    That and the way my coping is it would take a car dropping from the sky to have splash out.

    My water has been 85 degrees for about a week.

    The only other factor is the neighbors red pine drops tons of those orange/brown elbow macaroni shaped
    pollen nodules. I wonder if there is something in them that eats cya?

    I've done the cya test enough times (and have the 50ppm test solution) to know I have lost 30 CYA over 2 months.
    I just added more cya and back at 50 now.
    16x32 IG Vinyl, 13,000 Gals. Hayward S-244T sand filter, SP2810X15 pump
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    Re: CYA dropped to below 30

    I was literally just wondering this today. Mine was 80 45 days ago and now it is 50. My pool temp is heated and is 88 during day. Perhaps averages 85. Likely caused degradation if other thread is correct. I don't have a lot of splash out- certainly not that much.
    20k IG Irish Mist Pebble Sheen, Pentair IntelliFlo, Easy Touch, Clean and Clear 520, Solar Heating. Use Taylor K2006.

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    Re: CYA dropped to below 30

    Just brainstorming here. Is stabilizer identical in quality and composition? Since we are seeing a large number of CYA questions from experienced members, maybe there is variability in stabilizer behavior across manufacturers. Sort of a Good Witch vs Bad Witch situation.
    33k, IG Pebble, 1.5hp Challenger, Pentair FNS, TF-100

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    Re: CYA dropped to below 30

    Quote Originally Posted by frbruno64 View Post
    Just brainstorming here. Is stabilizer identical in quality and composition? Since we are seeing a large number of CYA questions from experienced members, maybe there is variability in stabilizer behavior across manufacturers. Sort of a Good Witch vs Bad Witch situation.
    i have been using the liquid $$ conditioner. I do loose around 1/4" of water every 1-2 days. Pool temp is a refreshing 94 degrees lol..
    IG Pebble sheen blue surf approx. 14k gallon, beach entry, 7' spa, 3.5 ton jumping rock/waterfall, Pentair 2hp whisper flo, booster pump, 520 cartridge filter, Stenner Econ T, 400k master temp heater, easy touch controls,TF-100 w/speedstir

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    Re: CYA dropped to below 30

    Didn't read all the replies but back washing your pump will lower your CYA because of removing the water. Evaporation won't.
    Inground 22k gallon gunite 15x31 main pool, 15x7 wading pool/sunning deck, hot tub/with overflow (9' octagon with limestone top) & slide NSWG, Aqua Blue Pebble Sheen
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    Re: CYA dropped to below 30

    I can add I've done zero back washes.

    Also, I finally test my CH. It was 250 ppm when cya was 50 and 2 months later is still 250 ppm.

    That would have gone down had I backwashed a few times. (it has in the past)

    So I definitely have some odd condition where my pool consumes 30 ppm of cya every 2 months.

    I have always used the 4lb container of chlorox stabilizer granules on amazon.
    This is my first season with this pool.

    Figured I would just post this all here instead of a new thread since most
    of us here have the mystery of cya going down.
    16x32 IG Vinyl, 13,000 Gals. Hayward S-244T sand filter, SP2810X15 pump
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