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Thread: what FC is safe to swim in? My AK is 210, Cya is 80

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    what FC is safe to swim in? My AK is 210, Cya is 80

    Hi I need advice. This is my second year of pool ownership and I have learned a lot already, but need to learn a lot MORE. I thought anything above Free Chlorine 3.0 was bad to swim in.

    This is my pool adventure for this year. We filled it up in May; it was great. At end of June, the lady behind us replaced her fence and flower beds, the dirt and saw dust went into my pool (our cover was ripped badly.) There was actual sawdust at bottom of pool that wouldn't vacumm up with teensy pool vacumm--- after two weeks I bought a Shop Vac and vaccumed it up, losing about 1/3 of the water. Filled it with city water. Then we went on vacation and came back to pool with a green tint, the pump/filter had shut off with the circuit breaker and chlorine tablets were gone anyway. So I put in chlorine tablets, that didn't help. I threw in half a packet of shock, that didn't help. I threw in the other half, that didn't help. I bought 60% algeacide, that killed the algae but now the water is cloudy. I added some clarifier, that didn't help. Then I came to the computer desperately searching for help. Now I have learned I shouldn't be throwing in every and all things I own just to try to fix the problem. So I got my test kit out (I usually use strips because my teenagers will do that but they hate the 'drops' stuff.) These are my numbers.
    Chlorine OTO is 5.0 bright yellow,
    PH 7.6 pink in the middle of the tube,
    Alkalinity is 21 drops (so that is 210 right?)
    The water hardness never showed blue even after I used all the drops in the kit so I don't know what went wrong. (We do have hard water -- I live in Utah - a desert state).
    My stabilizer test was 80 ppm which is high, right? I am guessing that is from throwing in shock stuff.
    We had over two weeks straight of 95 degrees or hotter during time it was full of sawdust but now temps are at 90 or so.
    So from what I read I need to make chlorine even more? But how do you tell how much chlorine you have when test tubes only goes to 5.0 and what is safe to swim in.
    Or do I just need to change filter cartridge if the cloud is from dead algae? I tried that two weeks ago and it didn't work and now I can't find a store that still has cartridges for my crappy Kmart filters. (end of season, apparantly)
    Any ideas of what to do next, and how soon can kids swim, and are there tests kits that are more specific, because I have a hard time guessing colors in tubes. Thanks, Tabby
    15 foot diameter round, 4600 gallon, above ground metal-framed vinyl pool with crappy filter/pump, no skimmer (- just me with leaf net), added extra pump/filter underwater inside, placed in full sun with no cover, no heater. Used 2x a week. Filled wtih new water May 2007.

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    JasonLion's Avatar
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    Often you can clean even the single use filter cartridges off with a garden hose, but there is a risk of ripping the filter paper. A pool store might well have a reusable filter that fits your system and I am sure you could order one over the Internet. Even a perfectly working filter can take several days to clear a cloudy pool after an algae bloom.

    With CYA of 80 you need to keep your FC level fairly high, 6 to 10, to keep your water safe and clear. There are better test kits, such as the TF Test Kit, see the link in my signature, which can measure much higher FC levels acurately. You can also try diluting the water sample one to one with distilled water and doubling the reading, but that is significantly less acurate.
    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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    "With CYA of 80 you need to keep your FC level fairly high, 6 to 10, to keep your water safe and clear. "

    So is it safe to swim at FC 6 to 10? Because the yellow OTO testing tube says 1.5 to 3.0 is "safe" which implies any higher is not. How high of a FC is dangerous and what would it do to hurt you? Burn skin? Rashes? I know high chlorine ruins swimwear elasticity besides bleaching colors.

    thanks for your advice! Tabby
    15 foot diameter round, 4600 gallon, above ground metal-framed vinyl pool with crappy filter/pump, no skimmer (- just me with leaf net), added extra pump/filter underwater inside, placed in full sun with no cover, no heater. Used 2x a week. Filled wtih new water May 2007.

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    duraleigh's Avatar
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    Go swimming. You're not close to fading suits or harming skin....you won't even know it's there.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    The "safe" level on the OTO test assumes a very low or non-existent level of CYA.

    CYA is like sunscreen for your chlorine. It keeps it from getting burned off by the sun as rapidly, so it is available to sanitize your water. However, it also decreases the effectiveness of the chlorine, as some of it is bound up with the CYA. Hence you need a higher residual chloring level to keep your water sanitary.

    About the worst high chlorine does is maybe sting the eyes a bit. I advocate that it is safe to swim in a high-chlorine pool (if the water is not green and there are no cc's) but rinse off promptly upon exiting. While in the water, the chlorine will not fade your suit or have other bad effects... it is when you get out and hit the air that it causes trouble! So wear an old suit and rinse well, and enjoy!!

    Read the stickies, found in my signature, for a better understanding of pool water chemistry and the BBB method.

    For now, you can dilute your pool water with 2 parts of distilled water and use that for your OTO test... multiply the result by 3. Now your kit reads to 15ppm, albeit less accurately. This method will tide you over until you can get a better test kit.

    8200 gallon 20' x 48" round vinyl frame pool, manually chlorinated with 10% liquid, salt added to ~2000, 12" sand filter, 1600gph pump, TF100 test kit
    Handy Links: PoolMath, TF-100 Test Kit, Pool School, Chlorine/CYA Chart
    "Shock" is a process, not a product!

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    I can assure you, not only from the chemistry involved, but from my wife's personal experience, that high Free Chlorine (FC) levels with high Cyanuric Acid (CYA) levels are perfectly safe. My wife swims at an indoor community pool during our 5-month "winter" season and swims in our own outdoor pool during the 7-month "summer" season. Her swimsuits degrade (rubber elastic loosens; some fading and these are "fade-resistant" swimsuits) over just ONE winter season of use while there is no sign of degradation whatsoever over multiple summer seasons (after about 4 summers, one starts to notice some slight degradation). The difference? The indoor pool does not use Cyanuric Acid (virtually no indoor pools do) and the Free Chlorine (FC) level I have measured has been around 2 ppm most of the time. In our own outdoor pool, the FC is from 3-5 ppm and the CYA is around 30 ppm.

    From a chemical point of view, 10 ppm FC with 80 ppm CYA has the same disinfecting chlorine (hypochlorous acid) level as 0.12 ppm FC with no CYA. 5 ppm FC with 30 ppm CYA has the same disinfecting chlorine level as 0.17 ppm FC with no CYA. So you can see how much less disinfecting chlorine there is in a pool with CYA compared to the indoor pool that has over 10 times the disinfecting chlorine level which would degrade swimsuits 10 times faster. Roughly speaking, pools with the same ratio of FC to CYA have similar amounts of disinfecting chlorine in them (the rule only works when the CYA level is much higher than the FC level as it is with the Min/Target levels we recommend).

    Richard
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
    12 Fafco solar panels; Purex Triton PowerMax 250 natural gas heater (200,000 BTU/hr output); automatic electric pool safety cover; 4-wheel pressure-side "The Pool Cleaner"

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    chem geek (or anyone else who knows),
    As far as safe chlorine levels for swimming, I'm guessing you can't go by the HOCl? For example, with CYA 0 and FC 3.0, the HOCl is 1.4, which is supposed to be safe for swimming. But to achieve that same level of HOCl at CYA 30 would require FC 24.0, which is way above shock level. It's obvious I'm missing something. If we could use HOCl as the determining factor for safe swimming, any idea what it would be?
    Poor Man's Pool
    Doughboy 18 ft round above ground
    7600 gal with center drain
    Pentair sand filter, 1 HP pump
    50 ppm borates
    "I know just enough to be dangerous"
    Pool Calc Ver 1.41 (Excel)

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    JasonLion's Avatar
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    Note: This is getting fairly technical. There is no need to worry about this stuff unless you want to understand the chemistry.

    I believe that HOCl around 1 starts causing problems for bathing suits across several months of swimming and somewhere around 2, or perhaps a little more, starts causing a few additional problems. HOCl around 10 can seriously damage metals. Most people will never get to a HOCl of 1, let alone 2, when using CYA.
    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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    I agree with Jason. And yes, shock levels which are around 0.3 ppm for HOCl for green algae and 0.7 ppm for shocking mustard/yellow algae are still below what is typically found in most indoor pools. This is one of the reasons I am trying to get CYA used in indoor pools, even at a low level (10-20 ppm CYA). I also believe it is one way to solve the problem of asthma and respiratory problems in competitive swimmers and small children in such indoor pools (since disinfection by-product reaction rates are related to HOCl concentration), but the industry mantra of "only chlorine matters; CYA doesn't matter" keeps getting in the way.

    OK, I'll stop ranting.
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
    12 Fafco solar panels; Purex Triton PowerMax 250 natural gas heater (200,000 BTU/hr output); automatic electric pool safety cover; 4-wheel pressure-side "The Pool Cleaner"

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    thanks everyone... now I am getting closer to understanding! Tabby
    15 foot diameter round, 4600 gallon, above ground metal-framed vinyl pool with crappy filter/pump, no skimmer (- just me with leaf net), added extra pump/filter underwater inside, placed in full sun with no cover, no heater. Used 2x a week. Filled wtih new water May 2007.

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