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Thread: Trying to understand why stabilizer is necessary

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    Kandi106's Avatar
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    Question Trying to understand why stabilizer is necessary

    I have been reading on here all about this topic. I understand that it is like a sunscreen for pools and it retains some chlorine, which helps to keep chlorine levels from going all over the place. My question is this: What does it matter if it helps retain chlorine if that chlorine is unavailable, which makes it useless other than to show up on ones pool test? It also requires that chlorine levels be kept higher, so I'm not quite sure how this is realistically helpful. Please explain!

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    Re: Trying to understand why stabilizer is necessary

    What does it matter if it helps retain chlorine if that chlorine is unavailable
    The chlorine is not unavailable. It is still there to do it's job but, with CYA it is not completely destroyed by the sun.
    Dave S.
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    Texas Splash's Avatar
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    Re: Trying to understand why stabilizer is necessary

    Hello and welcome to TFP! You may receive another more detailed explanation later, but I'll give you the basic version. Pools are required to maintain minimum standards for sanitation. There are a small handful of unique sanitary methods in existence, but by far the most common and accepted in the pool industry is chlorine - either by adding it manually or via a salt water generator. Without chlorine, the water becomes a breeding ground for bacteria. So now we have to determine how much chlorine is needed. Excluding indoor pools which are unique in their own right, regular outdoor pool's chlorine competes against two things - organics and sunlight. Where you live in the country determines how intense that sun will be, hence how much CYA is required. CYA and FC go together like PB&J as noted on the Chlorine/CYA Chart (link below). Some pools need a higher CYA because of the sun, so their FC must naturally be increased. But a pool should never be without chlorine (FC).

    Also important to note is the CYA, when balanced with the proper FC, buffers the effect of chlorine to make it safe for swimmers and pool liners. You'll also see this and many other items explained further in the Pool School's Pool School - ABCs of Pool Water Chemistry.

    So in summary, a pool needs chlorine to be sanitary. CYA protects the FC (to last longer) and makes the chlorine level safe for swimmers. Indoor pools don't have sun issues, so their levels are much lower. Some pools with solar covers may adjust differently as well. Hope this helps.
    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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    Kandi106's Avatar
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    Re: Trying to understand why stabilizer is necessary

    So, the chlorine that is left and not destroyed is just less effective, but still capable of disinfecting?

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    Texas Splash's Avatar
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    Re: Trying to understand why stabilizer is necessary

    I wouldn't say it's less effective, it's just a less amount. It's still disinfecting, but as that FC number gets lower it can be overwhelmed by organics. Chlorine is always being used and replaced. It's a constant cycle. So if you add bleach manually like I do, FC gets used to kill organics and fight the strong sunlight, then I replenish it each day. I don't lose it all of course, some continues to bind with CYA, but what is left is still productive and capable of sanitizing. So for me as an example....if my FC level was at 8 in the evening after adding bleach, then I used about 2.5 FC over the course of the next day which lowered it to 5.5, that remaining FC is still doing its job, but now I run the risk of being too low (based on that chlorine/CYA Chart). If not careful, the FC will not be strong enough to combat the organics and compete with the sun's UV. That Chlorine/CYA Chart is key to maintain water clarity and sanitation at various CYA levels based on the pool type and location.
    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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    Re: Trying to understand why stabilizer is necessary

    Quote Originally Posted by Kandi106 View Post
    So, the chlorine that is left and not destroyed is just less effective, but still capable of disinfecting?
    When you measure FC (free chlorine) you are actually measuring three forms of chlorine in your water -

    Chlorine bound to CYA (this is your reserve)

    Hypochlorous acid (powerful disinfectant and oxidizer)

    Hypochlorite ion (also disinfects and oxidizes but less so than hypochlorous acid)

    The hypochlorous acid and hypochlorite exist in balance with one another and the proportion of each relative to one another is determined by pH but they act together as your active chlorine (chlorine that kills and oxidizes). The total amount of active chlorine available is set by your CYA concentration. You only need a small amount of active chlorine in water to disinfect and oxidizes, ~0.10ppm (100 parts per billion) is more than enough to kill algae.

    As that active chlorine gets used up, more is released by the CYA so, in that sense, you CYA is acting as the reserve. Think of it like a battery discharging - once the chlorine bound to CYA starts to get exhausted, less and less active chlorine is released into the water. Once you drop below that 100ppb level of active chlorine, algae can start grow faster than it is killed.

    This why TFP recommends a minimum FC level based on your CYA level. Someone did all the complicated math to determine what levels of FC and CYA give you the active chlorine level of 0.1ppm. As long as you adhere to the standards we teach here, you will not have a problem.
    Matt
    16k IG PebbleTec pool, 650gal spa, spillway and waterfall, 3HP IntelliFlo VS / 1.5HP WhisperFlo, Pentair QuadDE-100 filter, IC40 SWCG, MasterTemp 400k BTU/hr NG heater, KreepyKrauly suction-side cleaner Dolphin S300i robot, EasyTouch controls, city water, K-1001, K-2006 and K-1766 test kits, Mannitol test for borates

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    Re: Trying to understand why stabilizer is necessary

    I'll just add one thing, which goes back to your question. Your tap water probably has around 1 or 2 ppm FC in it, and no CYA. If you put a glass in the sun, the FC will almost all be gone in around an hour (half life is around 30 minutes), because tap water has no CYA. The "harsh" part, the hypochlorous acid, is around half, so 0.5 to 1 ppm (more than we have in our pools).

    CYA gives the FC a longer half life in sunshine (more like 8 or 9 hours). So there's enough of it in the pool to last and absorb the other demands like bather load (killing bacteria, getting rid of ammonia, etc.). It is also moderating the "harshness", as JoyfulNoise explained. If you kept 1-2 PPM chlorine in your pool with no CYA, the harshness would be much higher, more like it is in tap water.
    12k IG salt; glass beads in plaster; K-2006C, K-1766, CCL, and Aussie 4in1 (HTH); Pentair Eco800 1.2HP VS; Zodiac SWC 1.3 lb/day (25 g/hr); 25" filter recycled glass; OKU solar panels; 1/2 HP solar pump; Rebel (Warrior) pool cleaner; FlowViz; prior pool AG 10k | Read Before Posting to get the best possible advice | ... and this helped me a lot!: TFPC for Beginners

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    Re: Trying to understand why stabilizer is necessary

    Ok, I understand. I was trying to do the least amount of chlorine possible because of a sensitivity to chemicals, but it sounds like without cya the chlorine would end up being more harsh. I have been using poly quat 60 at recommended doses and liquid chlorine, but it definitely is hard to control the chlorine. Pool looks clear and all levels are good, although the ph does fluctuate a little with the level of chlorine. I also have been pretty much babysitting my pool constantly.

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    Texas Splash's Avatar
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    Re: Trying to understand why stabilizer is necessary

    We have many, many members who arrive to TFP because of skin sensitivity issues. Many of them attributable to public pools and/or incorrect chemical management. Once they follow the Recommended Levels Chart (link below) they find their water to be very comfortable while remaining effective for sanitation. Hang around here long enough and you'll see what we mean. Simple grocery store products and clear water while saving you $$$. But remember, here at TFP ..... it's all about the right test kit. That's the foundation of everything here. Either a TF-100 (link below) or Taylor K-2006C. While I prefer the TF-100, we don't care which one you chose as long as you have one of those kits. Stay far away from the pool store and their magic potions and bottle of "fix-it-fast" remedies. They don't work. The proper test kit will tell you all you need to know. Your skin (and checkbook) will thank you.
    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.
    If you enjoyed your TFP experience, please consider donating to Support TFP!

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    Kandi106's Avatar
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    Re: Trying to understand why stabilizer is necessary

    I have been using tf-100. I just need to add stabilizer.

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    Zappafan's Avatar
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    Re: Trying to understand why stabilizer is necessary

    My partner is very sensitive to chemicals, she gets headaches from perfumes and aftershaves just by walking past a person wearing them, as well as issues from public pools in the past. She did not want me to use this method of manually chlorinating, but I talked her into letting me try it and she has never had any issues with it, in fact she loves it now. It works!
    17K Gallon,IG Vinyl,1hp Pentair Challenger,Pentair TA60 Sand Filter, Hayward Colorlogic,Re-lined 06-20-15, TF-100,SpeedStir,Lagunitas and Margaritas. Zappafan Pool Build

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    Re: Trying to understand why stabilizer is necessary

    If you've always gotten your advice from a pool store, what you hear here will be counter-intuitive. Largely because you've been sold snake oil for so long. Trust the advice here and everyone will love your pool. I keep my CYA at 70 and my FC at 5-7 and I never get complaints about chlorine smell (caused by CC and chloramines), burning eyes, bleached suits, green hair, etc.

    Meanwhile, I watch my neighbor (who I tried to help) fight all summer then hire a company who charges him a small fortune.
    My Pool: 18'x36' Grecian. Vinyl Liner, 500# sand filter, SWG.

    My hobbies: Brewing beer and flying rockets.

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