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Thread: CYA, FC and CC query!

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    CYA, FC and CC query!

    Hi all,

    Been in our new house with pool for 3 months now. I have just switched to the BBB method because the previous owner lived exclusively by the "5-pucks of stabilised chlorine and shock the pool once a week (with stabilised stuff) in the summer" method. My CYA levels are >100ppm. In fact, they are probably >200ppm because I diluted the pool water 50:50 with tap water and it still read at over 100ppm... YIKES. Yes, I'm probably supposed to drain the pool to drop the levels, but I'm hoping that backwashing the filter will gradually reduce the CYA.
    So my first question is: will backwashing really work and how many times will we have to backwash to reduce the CYA? The pool is nice and clean and we've only had to backwash the filter once so far!
    Secondly, if I have to drain the pool, can I use it to water the lawn? I don't want to just pour the water into the street. (Water is expensive and I feel guilty just throwing it away when it's so scarce here in California!).
    Thirdly, I know that excess CYA is 'bad' but seriously, how bad is it really?? The pool is clean and sparkly (with the exception of a few yellow algae spots on the warmest parts of the pool wall that I scrub off) so it can't be affecting the FC too much, can it?

    Which leads me to my fourth chemistry geek question:
    When you measure FC and CC with the Taylor K6000 kit, is the part of the total chlorine that is 'locked up' by the CYA measured by the kit? Does it fall under the FC or CC measurements? I just want to be sure that when I measure the chlorine and add bleach that I'm putting sufficient in there!

    I just got the Taylor kit (I was previously using Walmart's HTH 6-way kit) and here are my readings:
    - FC 0.6ppm (too low, I know, I added my bleach and will re-measure later!)
    - CC 0.2ppm
    - Alkalinity 220 ppm (the fill water is 190!)
    - Hardness ~1050ppm (fill water is 270ppm). Was hard to measure in the pool water because I had lots of pink floaters and got - the 'wandering endpoint' despite adding 5 drops titrant to the water before doing the test...
    - pH 8.0 (it used to hover between 7.5-7.8 when I was using the pucks but it's been steadily increasing since I switched to bleach. Fill water is pH 7.2-7.5. (I have to add 1.5 inches of water a week at the moment due to evaporation.). Just added 1lb dry acid and I'll re-measure tonight and assess the pH change. I'm aiming for pH7.5.
    - CYA >100ppm. Is there anything that can affect this test (i.e. high hardness?!) and give a false high reading? Just hoping!

    I'm still in the experimental stage of adding the right quantity of bleach frequently enough. Pool holds approx 10,000 gallons water. And I've been adding 50 fl oz 10% bleach about twice a week. Would I be better off adding less but more often? What is a typical schedule for adding bleach to an outside pool in the blazing Californian summer when your CYA is really really high?! I'm aiming to add enough to kick it up to 5ppm (because of the periodic spots of algae and knowing that it will drop quickly in the presence of ever-persisting sunshine). Is this about right?

    Last question: how long should you typically wait to swim once you've added a jug of bleach (with the pump running) and how long after adding acid? We usually have the pump running for 4 hours in the morning since we swim in the late afternoon, so I add my chemicals early in the day (I assume that my high CYA will protect the Cl from the sun!)

    Thanks for any input!
    12' x 20' kidney-shaped inground pool; one skimmer basket, 3 return jets.

    Purex Triton 'WhisperFlo' pump, model WFE-6, 1.5HP
    Purex Triton 2000 Series , model SMBW2072 (DE filter)
    Polaris 360 cleaner

  2. Back To Top    #2
    Richard320's Avatar
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    Re: CYA, FC and CC query!

    If the pool was clear now, it would be possible to maintain it despite astronomical CYA. I've done it. It's not easy. For starters, you will need a number for CYA. You might have to dilute more than 50-50. Maybe 2/3 tap water and 1/3 pool water, mix that, use it as your sample, then triple the reading. I had to maintain 22 ppm for several months. Didn't smell, didn't burn eyes, didn't bleach swimsuits, didn't use much bleach on a daily basis, but it sure took a lot to get it up to that level! In your case, since you have some algae, you'll need to shock. And fresh water will probably be cheaper than the amount of bleach you'll need.

    Your best bet is to drain and refill. I do it constantly, to lower my high CH, and my lawn hasn't died from using it there. Problem is, you're looking at draining more water in one shot than your yard can probably absorb. If you're near San Diego, you also have the option of reverse osmosis. But it will also probably cost more than the water.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
    A pool is like a pet - you have to feed it every day, even the days you don't want to play with it!

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    Re: CYA, FC and CC query!

    Thanks, Richard! I think I'll try diluting the pool sample and figure out exactly HOW much CYA we've got in there...
    12' x 20' kidney-shaped inground pool; one skimmer basket, 3 return jets.

    Purex Triton 'WhisperFlo' pump, model WFE-6, 1.5HP
    Purex Triton 2000 Series , model SMBW2072 (DE filter)
    Polaris 360 cleaner

  4. Back To Top    #4

    Re: CYA, FC and CC query!

    Oh, and how many ppm Cl should I aim for to shock with? Would 10ppm be enough? Thanks!
    12' x 20' kidney-shaped inground pool; one skimmer basket, 3 return jets.

    Purex Triton 'WhisperFlo' pump, model WFE-6, 1.5HP
    Purex Triton 2000 Series , model SMBW2072 (DE filter)
    Polaris 360 cleaner

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    UnderWaterVanya's Avatar
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    Jun 2012
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    Mint Hill, NC
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    2,589

    Re: CYA, FC and CC query!

    I think backwashing if you have > 200ppm is not going to make a dent in your CYA anytime within reason.
    Inlaws Pool Boy since June 14th 2012, Pool built ~ 2003, In-Ground, 16'x32'
    13500 gal, Vinyl Liner, Fiberglass Slide, TF-100 Test Kit, Hayward 210T
    sand filter, A.O. Smith 1.5HP main pump motor (C48L2N134C1),
    Hayward SuperPump (model ?), Polaris 380 & PB4 Booster Pump

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    Richard320's Avatar
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    San Dimas, CA (LA County)
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    Re: CYA, FC and CC query!

    Quote Originally Posted by vickiarmstrong
    Oh, and how many ppm Cl should I aim for to shock with? Would 10ppm be enough? Thanks!
    No. Not even close. pool-school/chlorine_cya_chart_shock If your CYA is 250, shock level will be something like 100. In your case, draining the majority of the water will end up cheaper and faster than trying to treat it. Don't forget your astronomical CH levels.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
    A pool is like a pet - you have to feed it every day, even the days you don't want to play with it!

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    linen's Avatar
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    Twin Cities, MN
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    Re: CYA, FC and CC query!

    Quote Originally Posted by vickiarmstrong
    Oh, and how many ppm Cl should I aim for to shock with? Would 10ppm be enough? Thanks!
    As Richard had said, if your cya is that high, and you have algae, it is not practical to do the shocking process until you lower the cya (shoot for 50 ppm), therefore you are going to have to do drain/refills.

    You signature doesn't say if your have a liner or a plaster pool.
    TFP Expert who uses Pool School and my TF100 test kit along with PoolMath for my: Round 11K gallon AGP with deep end, 20" sand filter, Matrix 1hp 2spd, 6 2ftX20ft solar panels (and solar cover!), Intex SWCG (copper bars disconnected) and a Rubadub hot tub (chlorine). The SLAM process is not finished until: 1. CC < 0.5 ppm, 2. An OCLT < 1.0 ppm and, 3. The water is crystal clear.

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