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Thread: CYA level decreases without too much water replacement

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    CYA level decreases without too much water replacement

    I was keep my pump off for almost a week because I tried to figure out where the slow leakage is. So within the week, I kind of replace 2-3 inches of water. (The pool averagely is about 5 feet deep). My CYA level was 37 one week ago, and today it is 22. (FC is almost 0 and CC is 1. Ph & TA are good). I thought that CYA won't be decreased unless water is replaced. But how can my CYA level drops dis-proportionally? (btw, my pool has full sunshine. and during this week, long island has been pretty hot. >80F with everyday being sunny.) (The test result is from one of the local pool store and should be pretty accurate.)

    One more question, for my case, do you think I need to shock the pool once? the water is pretty clear btw.

    thank you.
    20'x 40' 32000 gallon pool. (built approx in 2001.)
    Vinyl liner (replaced in 2017)
    Pentair FNS Plus 48 DE filter
    AutoPilot Salt Chlorine Generator.
    Pentair Whisperflow pump w/ Variable Speed V-Green 165 Pool Pump Replacement Motor

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    Mod Squad tim5055's Avatar
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    Re: CYA level decreases without too much water replacement

    How are you testing that you get the results 37 or 22? Pool Store?
    TFP Moderator 39 X 18 23,000(ish) freeform gunite; built 2007ish; Pentair Triton II TR100 600lb Sand filter; 2 HP Pentair pump with 2.2 HP AO Smith single speed motor; 2 skimmers, 1 main drain, 4 returns w/waterfall, Stenner 45MHP2 3GPD running@ 60% - 15 gal Tank; heated by the sun CYA 200+ when I started - 50 now. Dolphin Supreme M5 Pool Cleaner. Hot Springs SX Spa, 285 gallon

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    Re: CYA level decreases without too much water replacement

    Yes. Both numbers are from the same pool store. thank you.
    20'x 40' 32000 gallon pool. (built approx in 2001.)
    Vinyl liner (replaced in 2017)
    Pentair FNS Plus 48 DE filter
    AutoPilot Salt Chlorine Generator.
    Pentair Whisperflow pump w/ Variable Speed V-Green 165 Pool Pump Replacement Motor

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    AimeeH's Avatar
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    Re: CYA level decreases without too much water replacement

    We don't generally trust pool store testing and prefer to see test numbers from your own test kit. I'd reccomend the TF-100 but you could take a look here. Pool School - Test Kits Compared

    CYA is one that pool stores often get wrong.

    Should you shock pool once? No. Here at TFP we use the term SLAM (Shock Level And Maintain) if you have algae or cloudy pool that needs to be cleaned up. It is a process not a product. Other say "shock" usually in reference to a one time heavier dose of chlorine which we don't advocate.

    Consider getting a test kit and you will be able to learn what your pool needs and not have a clerk at the pool store sell you what they need to sell you. It will save you $$$$ in the long run.
    18*36*23 true "L" vinyl IG 29,000 gallons. SWG. TF-100 test kit.
    http://tftestkits.net/splash-page.html

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    Re: CYA level decreases without too much water replacement

    Right. Sorry for my term. I meant if I need to SLAM it considering my current situation. (There is definitely no obvious algae or cloudy water. Just CC is 1 and FC is almost 0. ) If not SLAM, can you please suggest a way to decrease CC and increase FC back in regular range?

    I do have a Taylor K-2006 kit. I will definitely do CYA test in a while myself. (I have been had a feeling that pool store reading should be more accurate than myself. Maybe I am wrong.)

    thank you very much.
    20'x 40' 32000 gallon pool. (built approx in 2001.)
    Vinyl liner (replaced in 2017)
    Pentair FNS Plus 48 DE filter
    AutoPilot Salt Chlorine Generator.
    Pentair Whisperflow pump w/ Variable Speed V-Green 165 Pool Pump Replacement Motor

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    Re: CYA level decreases without too much water replacement

    Quote Originally Posted by bfang711 View Post
    Right. Sorry for my term. I meant if I need to SLAM it considering my current situation. (There is definitely no obvious algae or cloudy water. Just CC is 1 and FC is almost 0. ) If not SLAM, can you please suggest a way to decrease CC and increase FC back in regular range?

    I do have a Taylor K-2006 kit. I will definitely do CYA test in a while myself. (I have been had a feeling that pool store reading should be more accurate than myself. Maybe I am wrong.)

    thank you very much.
    We trust your test more than the pool store

    How are you currently chlorinating?

    Could you add your pool information into your signature? That helps us. Trouble Free Pool
    18*36*23 true "L" vinyl IG 29,000 gallons. SWG. TF-100 test kit.
    http://tftestkits.net/splash-page.html

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    Re: CYA level decreases without too much water replacement

    I just added the info in my signature. hope it will help. Yes. I use Pentair 320 inline chlorinating feeder w/ high flo kit. It was half full couple of days ago, and today it is like almost gone. I just refill with 3" trichlo tabs.

    I tested CYA just now using Taylor K-2006. It is around 30. (Taylor K2006 should have given more CYA test reagent. I probably have only one time test of CYA left. )

    Do you think I can add in some liquid chlorine tonight to bring up the value? and if yes, what value should I bring up to? to 4 the regular level or to 12 the shock level?

    thank you again.

    There was an error in the signature. Corrected it.
    20'x 40' 32000 gallon pool. (built approx in 2001.)
    Vinyl liner (replaced in 2017)
    Pentair FNS Plus 48 DE filter
    AutoPilot Salt Chlorine Generator.
    Pentair Whisperflow pump w/ Variable Speed V-Green 165 Pool Pump Replacement Motor

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    Mod Squad tim5055's Avatar
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    Re: CYA level decreases without too much water replacement

    We don't do one time shocks. We either SLAM the pool if there is a problem or we maintain the proper FC/CYA ratio if there is not a problem. To determine if there is a problem we perform the Overnight Chlorine Loss Test

    If you continue to use the puck chlorinator your CYA is going to go up quickly. Each tab is almost half CYA.

    Use bleach to get your FC above 5 and do an Overnight Chlorine Loss Test tonight.

    The chlorinator must be turned off for the test.
    TFP Moderator 39 X 18 23,000(ish) freeform gunite; built 2007ish; Pentair Triton II TR100 600lb Sand filter; 2 HP Pentair pump with 2.2 HP AO Smith single speed motor; 2 skimmers, 1 main drain, 4 returns w/waterfall, Stenner 45MHP2 3GPD running@ 60% - 15 gal Tank; heated by the sun CYA 200+ when I started - 50 now. Dolphin Supreme M5 Pool Cleaner. Hot Springs SX Spa, 285 gallon

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    Re: CYA level decreases without too much water replacement

    Got it. I will do the OCLT test tonight and post results in here.

    btw, I just searched inside the forum about the puck chlorinator and the high CYA issue of using it. Is there any chlorine tab in the market that has chlorine only without CYA, just in case my CYA level goes up, although it has been still in a low level.

    thank you very much.
    20'x 40' 32000 gallon pool. (built approx in 2001.)
    Vinyl liner (replaced in 2017)
    Pentair FNS Plus 48 DE filter
    AutoPilot Salt Chlorine Generator.
    Pentair Whisperflow pump w/ Variable Speed V-Green 165 Pool Pump Replacement Motor

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    Re: CYA level decreases without too much water replacement

    Quote Originally Posted by bfang711 View Post
    Got it. I will do the OCLT test tonight and post results in here.

    btw, I just searched inside the forum about the puck chlorinator and the high CYA issue of using it. Is there any chlorine tab in the market that has chlorine only without CYA, just in case my CYA level goes up, although it has been still in a low level.

    thank you very much.
    No. All "dry" or granular chlorine is stabilized by either CYA or calcium (Cala-hypo powder). Liquid chlorine is what you'll need once your CYA gets high unless you can stomach draining and refilling........or going the SWG route.
    18*36*23 true "L" vinyl IG 29,000 gallons. SWG. TF-100 test kit.
    http://tftestkits.net/splash-page.html

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    Mod Squad pooldv's Avatar
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    Re: CYA level decreases without too much water replacement

    More here on chlorine products, Pool School - How to Chlorinate Your Pool
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    If TFP helped you or saved you money - Become a TFP Supporter! <--Click here
    2012 build and pics, 20k gal gunite, black onyx pebblesheen, OK flagstone, IntellifoVS, cart filter w/Pleatco, IC40 SWG, Solartouch, 5 12'x4' solar panels, HP50HA heat pump, 8mil solar cover, borates, TF-100 test kit, SONOS, Doheny's Discovery Robot, hot tub on bleach

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    Re: CYA level decreases without too much water replacement

    Just finished pouring a little less than 2gallon of 10% liquid chlorine and bring up the FC to 3.5. I will leave it for tonight and retest tomorrow morning.

    May I ask if I use the liquid chlorine way, does it mean that I have to pour in the chlorine in a daily basis, which will be a serious job in some sense? Or it doesn't have to be a daily job. I think twice a week for pool maintenance would be something I can stay with, like doing water testing, brushing and vaccumming etc, etc.

    Because of the budget, I would consider change to SWG in couple of years probably.
    20'x 40' 32000 gallon pool. (built approx in 2001.)
    Vinyl liner (replaced in 2017)
    Pentair FNS Plus 48 DE filter
    AutoPilot Salt Chlorine Generator.
    Pentair Whisperflow pump w/ Variable Speed V-Green 165 Pool Pump Replacement Motor

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    Re: CYA level decreases without too much water replacement

    That link is very helpful. thanks.

    It says to add 2-3ppm of chlorine daily if I choose to use the liquid chlorine way. Is that possible that I add in once to bring it up to 9ppm, and it can stay for 3 days. This way I don;t have to do it every day, unless there is some drawback to the pool itself by doing this. I don't know if it makes sense. Correct me please if I am wrong.

    thank you.
    20'x 40' 32000 gallon pool. (built approx in 2001.)
    Vinyl liner (replaced in 2017)
    Pentair FNS Plus 48 DE filter
    AutoPilot Salt Chlorine Generator.
    Pentair Whisperflow pump w/ Variable Speed V-Green 165 Pool Pump Replacement Motor

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    Re: CYA level decreases without too much water replacement

    Quote Originally Posted by bfang711 View Post
    May I ask if I use the liquid chlorine way, does it mean that I have to pour in the chlorine in a daily basis, which will be a serious job in some sense?
    Yes, liquid chlorine is a daily task. But, you can get a dosing pump to add liquid chlorine automatically. Then you just have to fill the tank from time to time. Do a forum search for Stenner Pump to see some stories about it.
    29,000 gallon vinyl liner custom designed lagoon style in-ground pool (self-built 2015-2016), Hayward EcoStar VS pump, Hayward HP21404T Heat Pump (140K BTU), Hayward Pro Grid DE DE6020 Filter with Fiber Clear, Hayward Tiger Shark, 2 Hayward Color-Logic LED lights, Stenner 45MPHP10
    370 gallon Jacuzzi J-345 spa with ClearRay UV

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