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Thread: Need Help- SLAM/Shock and still can't get FC to hold

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    Need Help- SLAM/Shock and still can't get FC to hold

    37,000 gallon gunite pool. Recently switched to salt water. Water is clear, but has a slight green haze that can be seen at night with light on. I don't have a good test kit yet, but testing with various strips and at the pool store. pH and alkalinity are good, and stabilizer is around 50. But FC isn't holding. This morning I put 9 bottles (121 oz) of 8.25% bleach in at 6:30 am. This was based on the pool calculator, trying to get FC to 15. Reading on strips was off the chart. By noon same day, FC was 0. Added 9 more bottles. At 4:30 pm today, FC is back to 0. *** is happening? Did I do my math wrong? 18 bottles in less than 12 hours, gone. Before I buy every bottle from walmart again, hoping someone can provide some advice.
    37,000 gal IG concrete free-form, Hayward TriStar VS pump, Sta-Rite System 3 cartridge filter, Polaris w/ booster pump, CircuPool RJ60g SWG, Hayward OnCommand w/ remote

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    Re: Need Help- SLAM/Shock and still can't get FC to hold

    I was having the same problem with disappearing FC. I'd dump a jug of bleach one evening and it'd all be gone by morning. From what I learned on here, there are only two things that can gobble up FC so fast:

    1. Sun light
    2. Algae

    To rule out sunlight, do an OFCT and if FC is lower in the morning than the previous evening, you have an algae problem - which you continue SLAMing until

    1. OFCT = 0
    2. The water is clear
    3. CC < 0.5

    I am trying to do the same thing myself. Oh btw, I did read somewhere on here that test trips are unreliable.
    IG gunite pool size: 12,500 gallons - includes spa with spillover, Polaris vacuum cleaner, Ultrapure Ozonator, inline tab chlorinator that I no longer use
    Filter: Hayward Swimclear Model #4030, 4-Cartridge Filters
    Pump: Century, 2 HP with a Hayward 6060 booster pump
    Date of build: March-April 2014 *NEW* : Test kit: TF-100

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    Re: Need Help- SLAM/Shock and still can't get FC to hold

    Thanks. Have done a lot of reading on here as well, learned a lot. I just can't seem to understand how 18 bottles of bleach has disappeared in less than 12 hours. Trying to follow the SLAM method and use the calculators, but I still can't get the FC to hold. Straight back to 0. Very frustrating (and costly).
    37,000 gal IG concrete free-form, Hayward TriStar VS pump, Sta-Rite System 3 cartridge filter, Polaris w/ booster pump, CircuPool RJ60g SWG, Hayward OnCommand w/ remote

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    Richard320's Avatar
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    Re: Need Help- SLAM/Shock and still can't get FC to hold

    yardoasis is right.... but you can't do the overnight loss test without a proper test kit.

    If your pool has no CYA, just about anything you dump in the pool will be gone to sunlight in a few hours.

    On the other hand, really high FC levels can actually bleach out the test strip and make you think there is no chlorine when there's actually lots and lots. It will bleach out a DPD test kit, too. That's the one with chlorine on one side and pH on the other using shades of pink. The FAS-DPD chlorine test will work up to 50, and be accurate to .2 ppm. The OTO (yellow) chlorine test won't bleach out, but is only calibrated to 5. You get both the good tests in a TF100. Best investment you'll ever make. My pool is so trouble-free I have time to spend here answering questions. I test myself with a TF100. Coincidence? I think not!
    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: Need Help- SLAM/Shock and still can't get FC to hold

    Guessing the website sells these test kits? Just ordered mine. Any suggestions until it comes in?
    37,000 gal IG concrete free-form, Hayward TriStar VS pump, Sta-Rite System 3 cartridge filter, Polaris w/ booster pump, CircuPool RJ60g SWG, Hayward OnCommand w/ remote

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    Re: Need Help- SLAM/Shock and still can't get FC to hold

    Read through pool school, repeat several times. Also read up on SLAM process and repeat several times.
    12000 Gallon IG Plaster built 2/15/2014. Jandy 340 sg ft 127 gpm filter, Jandy 1 HP stealth pump. Circupool RJ-45 SWG (overkill). TF-100 with Speed Stir.

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    Re: Need Help- SLAM/Shock and still can't get FC to hold

    I've read through it several times, thanks. Again, can anyone look at my math? Pool store tested CYA at 58, so I was close at 50. Based on calculator, I showed needing 8.9 bottles. But each time, the FC was zero within 4 hours. $60 gone today. Do I do it again tomorrow? Use even more? Just trying to figure out my mistake.

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    Richard320's Avatar
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    Re: Need Help- SLAM/Shock and still can't get FC to hold

    Quote Originally Posted by mattttt25 View Post
    I've read through it several times, thanks. Again, can anyone look at my math? Pool store tested CYA at 58, so I was close at 50. Based on calculator, I showed needing 8.9 bottles. But each time, the FC was zero within 4 hours. $60 gone today. Do I do it again tomorrow? Use even more? Just trying to figure out my mistake.
    Problem One: You're trying to do it with test strips. In the SLAM article --which you've read several times-- it says
    Prerequisites:
    • You need to have a FAS-DPD chlorine test
    If we had a CC reading, maybe we could tell if some CYA converted to Ammonia over the winter. That will create a HUGE appetite for bleach. But test strips can't test that.

    Problem Two: "Pool store tested CYA at 58" Pool store testing is notoriously unreliable, and the CYA test least reliable of all. Here's a post by a guy who had the CYA test 23 and 80 at the same store one day apart and he didn't add any!

    Next up: do the test strips ever show chlorine, or are they bleaching out? You could be driving FC from 35 to 50 and reading zero the whole time because it's bleaching things out!

    It's like you're painting while wearing a blindfold. Get a test kit, get some believable numbers, and from then it should be easy.
    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: Need Help- SLAM/Shock and still can't get FC to hold

    I was in a similar situation a couple of weeks ago, waited for my kit and have gone so far and saved so much! It works if you work it. When my kit arrived I was overwhelmed but after a few tests and lots of advise it became clear. Good luck and hang in there!
    Quote Originally Posted by mattttt25 View Post
    I've read through it several times, thanks. Again, can anyone look at my math? Pool store tested CYA at 58, so I was close at 50. Based on calculator, I showed needing 8.9 bottles. But each time, the FC was zero within 4 hours. $60 gone today. Do I do it again tomorrow? Use even more? Just trying to figure out my mistake.
    13,500 gal, installed 2006, vinyl, 24' round, AG - sand filter, 1.5 hp pump, TF-100 test kit w/ SpeedStir
    Lower NC

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    Re: Need Help- SLAM/Shock and still can't get FC to hold

    I ordered the test kit. Sorry, didn't pay the $30 for 2day shipping. Once it's here, I'll post all the results I get. Until then, all I have is test strips and store. After adding chlorine this morning, the strip indicated extremely high chlorine. Slightly low pH and alkalinity. CYA of around 50. 4 hours later, same results except FC was zero. Hit it again. Same results again. And 4 hours later, back to zero FC. Sent wife to store, just to try and confirm some numbers. They confirmed no FC and CYA of 58. I understand the kit results are the only ones you're gonna trust, but in absence of having them, the strips and store have provided the same numbers.

    I was heading back to Walmart at 6 am tomorrow, hoping they got more bleach, and planned on hitting it even harder tomorrow. Wasting my time? Is it really better to just let the pool go and wait for the kit? Or do I give it another shot, maybe 12 bottles this time. No clue.

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    Richard320's Avatar
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    Re: Need Help- SLAM/Shock and still can't get FC to hold

    If you have ammonia, it's going to take a huge amount of bleach to neutralize it.

    chloroxtanker.jpg
    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: Need Help- SLAM/Shock and still can't get FC to hold

    I just can't seem to understand how 18 bottles of bleach has disappeared in less than 12 hours
    Always, Always remember that only two things consume chlorine in your pool....sunlight and organics.

    If you consume 18 or 180, or even 1800 bottles of chlorine, it is not a mistake on your part.......it is because they are being consumed by sunlight and the organics in your pool.

    Once you kill the organics and get the correct amount of CYA to offer protection from the sun, your pool's voracious appetite will drop dramatically.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
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    Re: Need Help- SLAM/Shock and still can't get FC to hold

    Remember to brush the pool daily during the slam. You may also want to check behind pool ladders and light niches. They are hiding places for algae.
    TFP Moderator
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    Re: Need Help- SLAM/Shock and still can't get FC to hold

    OK, well I guess I'm stuck until the test kit comes in. Reading more about CYA and ammonia, it sounds they that could have happened. When I opened the pool, my CYA was around 100, so it seems like it's disappeared. The pool is actually crystal clear right now after yesterday's "shock", but still not holding chlorine. If I do have ammonia, my shock level yesterday could have been only half of what was needed.

    I'll wait for the test kit. I will let the chlorine generator run, at least I'm putting some chlorine in the pool on a regular basis. I also plan on getting the pH and alkalinity up, since both are slightly low. Will also stock up on bleach and be ready for whatever comes next. Thanks-

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    Re: Need Help- SLAM/Shock and still can't get FC to hold

    Richard- you're killing me with the graphics today! First the Wheel of Fortune elsewhere then the Clorox truck here!
    18'x38' Rectangle (3'-8 1/2' deep w/ diving board) - 27K gal. w/ gray plaster
    Hayward equipment (cartridge filter, 2-speed pump, SWCG, automation) View Our Build
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    Re: Need Help- SLAM/Shock and still can't get FC to hold

    Stick around, it gets better. Youtube clips, memes, and even a random Dr. Nick reference a few months ago.
    33' round, 23,000 gal AG vinyl , 1HP 2spd PowerFlo Matrix downsized with 3/4HP impeller (X2), Hayward S180T 150# sand filter (X2), Hayward H250 NG heater Pool Store year 1 - $850 for 2 months; Pool Store year 2 - $440 for 2 months, TFPC year 1 - $170 for 4 months; TFPC year 2 - $95 for 4.5 months
    The most important article on this site - The ABCs of Pool Water Chemistry

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    Re: Need Help- SLAM/Shock and still can't get FC to hold

    I'm even impressed that he changed the UN ID number on the placard to 1791, which is for Hypochlorite solutions. Attention to details....a true TFP'r.
    15'x30' IG - Roman-style - 14K - Pebble Fina Classico
    Filter: Jandy CL460 Pump: Jandy Stealth SHPF1.5 SWG: Jandy AquaPure 1400 Cleaner: Jandy RayVac Test Kit: TF-100 w/SpeedStir

    Chlorine/CYA Chart----Extended Test Kit Directions----SLAM

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    Re: Need Help- SLAM/Shock and still can't get FC to hold

    UPDATE: Got my test kit today, but first, what have I done since last week. I couldn't sit around and let this thing win, especially with the holiday weekend approaching. Wife called me one day and said Kmart was running a sale on Tri-Chlor shock at 58%. I was thinking my CYA was low at the time, so I decided to go all in. Put 30 lbs of shock in Friday night, 10 lbs every two hours. FC was off the chart with strips. That morning, I was reading a FC at between 5-10. Not great, but it was the first time this year I actually held chlorine. Pool became clear and a light shade of blue. I added a gallon or two of liquid chlorine each night, ran the SWG, and was able to at least measure some chlorine each day. Had a great holiday weekend with lots of swimming. Yesterday, had about 20 kids and 15 adults in the pool all day into the evening. I put one gallon in before bed.

    On to the test results, taken around 7 pm tonight:

    FYI, I ran the chlorine tests twice, so I'm reporting both results.

    FC 4.0/3.5
    CC 1.0/1.0
    TC 5.0/4.5
    CH 325 ppm
    TA 80
    CYA 100
    pH 6.8
    Salinity 2545 ppm (my SWG says salt good?)

    Suggestions? What should I address first? Thanks in advance-
    Last edited by mattttt25; 05-27-2014 at 09:08 PM. Reason: spelling & number error
    37,000 gal IG concrete free-form, Hayward TriStar VS pump, Sta-Rite System 3 cartridge filter, Polaris w/ booster pump, CircuPool RJ60g SWG, Hayward OnCommand w/ remote

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    Richard320's Avatar
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    Re: Need Help- SLAM/Shock and still can't get FC to hold

    Quote Originally Posted by mattttt25 View Post
    UPDATE: Got my test kit today, but first, what have I done since last week. I couldn't sit around and let this thing win, especially with the holiday weekend approaching. Wife called me one day and said Kmart was running a sale on Tri-Chlor shock at 58%. I was thinking my CYA was low at the time, so I decided to go all in. Put 30 lbs of shock in Friday night, 10 lbs every two hours. FC was off the chart with strips. That morning, I was reading a FC at between 5-10. Not great, but it was the first time this year I actually held chlorine. Pool became clear and a light shade of blue. I added a gallon or two of liquid chlorine each night, ran the SWG, and was able to at least measure some chlorine each day. Had a great holiday weekend with lots of swimming. Yesterday, had about 20 kids and 15 adults in the pool all day into the evening. I put one gallon in before bed.

    On to the test results, taken around 7 pm tonight:

    FYI, I ran the chlorine tests twice, so I'm reporting both results.

    FC 4.0/3.0
    CC 1.0/1.0
    TC 5.0/4.5
    CH 325 ppm
    TA 80
    CYA 100
    pH 6.8
    Salinity 2545 ppm (my SWG says salt good?)

    Suggestions? What should I address first? Thanks in advance-
    Four things pop out: Fc too low for the CYA level; CC level is too high, CYA is too high; pH is too low.

    The high CC indicates the need for a SLAM still exists. However, the CYA level is so high, it makes that difficult. So a partial drain is called for. 30 lbs of trichlor was waaaaay to much. Your pH needs to be raised, since the trichlor drove it too far down, but if you're going to drain some, why adjust the pH only to pump the stuff out? And whatever you do, a SLAM is next up. With bleach only this time.

    In order, I'd say: drain 30-40%, adjust pH, SLAM it.
    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: Need Help- SLAM/Shock and still can't get FC to hold

    I would say the CC shows you are definitely fighting something. But with CYA of 100, your FC is low, you probably should still be at SLAM level because of the CCs.
    26' X 52" Intex Ultra Frame. Intex Sand Filter
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    You can lead a horse to (clear) water, but you can't force him to swim in it!

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