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Thread: FC not dropping like normal during "Slam"

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    FC not dropping like normal during "Slam"

    I am opening my pool and began the big "Slam" session today. My CYA was 30 & PH was 7.3, so I added the amount of bleach required to reach shock level. Then I tested the FC level after 30 minutes and it had not changed. So, I waited another 30 minutes, and again, the FC level had not dropped. After another 2 hours, the FC level dropped a tiny bit, but I wouldn't say even a full point.

    Last year was my first time to maintain my pool this way, but I remember it took several incremental additions of bleach before the FC level began maintaining for any length of time. So, I expected a substantial drop when I tested it. Since I have never dealt with this, I'm just wondering if there is something I do not know/understand. Or, if this is not something out of the ordinary, how do I proceed? Do I just keep testing it every 30 minutes, & when I finally see a drop, add the appropriate amount of bleach to get the FC back to shock level?

    Thank you! Not sure what I would do without all of the info I get from you guys!

    6000 Gallons; Vinyl; AG; Columbia High Performance Sand Filter, 200 lb, 2 HP, 6,000 GPH; Krystal Clear SWG; 3 years old; Using TF-100 Test Kit.

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    Mod Squad tim5055's Avatar
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    Re: FC not dropping like normal during "Slam"

    What does the water look like?

    If it is clear, wonderful.

    Not every pool needs to have a SLAM when it is opened. If it is clear, conduct an Overnight FC Loss Test (OCLT) and report the results in the morning. If you have less then 1.0 ppm drop in FC overnight you are done.
    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: FC not dropping like normal during "Slam"

    I had alot of algae (and tadpoles), when I opened the pool. So, it is not clear yet, but the green has faded significantly. After I tested it this last time, and saw the green had faded quite a bit, I brushed the pool well. I am still testing every 30 min, and am due to test again in about 10 min.

    6000 Gallons; Vinyl; AG; Columbia High Performance Sand Filter, 200 lb, 2 HP, 6,000 GPH; Krystal Clear SWG; 3 years old; Using TF-100 Test Kit.

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    Mod Squad tim5055's Avatar
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    Re: FC not dropping like normal during "Slam"

    Green with tadpoles I would expect to consume chlorine. Could your reagents be bad/old?
    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: FC not dropping like normal during "Slam"

    I bought them towards the end of last season. Would they go bad that quickly?

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    Re: FC not dropping like normal during "Slam"

    Okay, when I tested my water this morning, the FC had finally dropped some. It dropped from 10 to 7. Hoping that means my regents are not bad...

    6000 Gallons; Vinyl; AG; Columbia High Performance Sand Filter, 200 lb, 2 HP, 6,000 GPH; Krystal Clear SWG; 3 years old; Using TF-100 Test Kit.

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    Mod Squad tim5055's Avatar
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    Re: FC not dropping like normal during "Slam"

    They are usually good for a couple of years if stored properly.

    OK, lets add chlorine to bring it back to shock level.

    Brush the pool and repeat
    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: FC not dropping like normal during "Slam"

    I like to test my reagents before I start to rely on them. I'll add a couple of drops of bleach to a glass of water and see if they respond like they should, repeating with baking soda, then Borax. I usually at least get a new bottle of strips each year, my test kit usually every other year. I normally run out, before they get old.

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    Re: FC not dropping like normal during "Slam"

    Quote Originally Posted by tim5055 View Post
    They are usually good for a couple of years if stored properly.

    OK, lets add chlorine to bring it back to shock level.

    Brush the pool and repeat
    Quote Originally Posted by tim5055 View Post
    They are usually good for a couple of years if stored properly.

    OK, lets add chlorine to bring it back to shock level.

    Brush the pool and repeat
    My reagents are less than a year old, and I think I've taken good care of them. So, they should be good.

    Okay, I did as you recommended. Here is a rundown of what the day looked like.

    8:30 am - Brought it back to shock level (10 based on PoolMath tool), & brushed the pool.
    9:30 - FC = 9, brought to shock level & brushed
    10:30 - FC = 7, repeated shock/brush
    11:30 - FC still 10, so I did not add anything
    I had to leave for a few hours.
    Returned at 5:00 pm - FC = 7, shocked/brushed
    6:00 - FC still 10
    7:00 - FC = 9, shocked/brushed
    8:00 - FC = 9, shocked/brushed
    9:00 - FC = 9, shocked/brushed

    Overall, I am not seeing a big FC drop between testings, but there is still a drop of at least one point usually. The algae is continuing to fade, but the water is definitely not clear. Still cannot see the bottom of the pool. I do know it takes time for the water to clear completely.

    I am having such a different experience this year, so I'm just not confident about how to proceed. Do I continue to test every hour or so & adjust to shock level? Or do I return it to shock level for the night & see where it stands in the morning?

    (FYI, my CYA is super low. My husband changed a hose fitting yesterday morning. After he went back inside the house, the hose slipped off & we lost quite a bit of water before he saw what was happening. The CYA was at the minimal acceptable level already, & replacing the lost water caused the CYA to drop to almost nothing. I could not get any locally, & had to order it. So I will address the CYA first chance I get.)

    6000 Gallons; Vinyl; AG; Columbia High Performance Sand Filter, 200 lb, 2 HP, 6,000 GPH; Krystal Clear SWG; 3 years old; Using TF-100 Test Kit.

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    Mod Squad kimkats's Avatar
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    Re: FC not dropping like normal during "Slam"

    I would test less often as you are not seeing big drops. I would say every other hour or so.

    If you add DE to your sand filter it will help clear your water faster. The only thing is that it has to be "babysat" so the pressure does not go too high. Here is a link to how to do it.

    Pool School - Add DE to a Sand Filter

    Use care when you add it as it should not be breathed in.

    Good luck! Let us know how it is going!

    Kim
    TFP Moderator 33x52 round AG 25,600 gals Sand Filter 1.5hp Pump - 2 Speed, SLAM, Pool School, Recommended Levels, Recommended Chemicals, Pool Math, Chlorine/CYA Chart, TF-100 Test Kit

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    Re: FC not dropping like normal during "Slam"

    Patience and perseverance! Hang in there. Although if your CYA dropped (or is possible) due to a significant loss of water that is important. I would suggest you check your CYA immediately to see if you need to adjust it to a new FC SLAM Level based on the Chlorine/CYA chart link below. Stay with it!
    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
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    Re: FC not dropping like normal during "Slam"

    Thanks for sticking with me guys! Sorry if my questions are wordy...

    Water is continuing to improve gradually. Now seeing a FC drop of about 1.5 over the course of 3-4 hours.

    I finally got a supply of CYA (stabilizer), so I am ready to address this issue now.

    Question #1
    Tested the CYA level. At the 30 mark, the water is still clear & the black dot is easily visible. Should I proceed as if the pool has nearly no CYA? Calculate the amount needed to raise CYA to the recommended level, & then back off just a little in case my true level is not totally zero?

    Question #2
    What is my goal CYA level? When looking it up, I realized that I need clarification about what figures to use when calculating my goal CYA & other chem levels. For ex., on the Chlorine/CYA Chart, I see that there is a bleach chart & an SWG chart. I do have an SWG, but will not start running it until I am done slamming. Currently, my sole source of chlorine is bleach. So, for now, do I do all calculations based on a "bleach" pool, & then switch to SWG pool calculations once I start running the SWG? I see that the recommended CYA level is higher for SWG versus bleach. Looks like 30 for bleach & 70 for SWG? Do I aim for 30 at this point? If so, will I need to increase the CYA level once I begin using the SWG as my primary source of chlorine?

    6000 Gallons; Vinyl; AG; Columbia High Performance Sand Filter, 200 lb, 2 HP, 6,000 GPH; Krystal Clear SWG; 3 years old; Using TF-100 Test Kit.

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    Re: FC not dropping like normal during "Slam"

    Quote Originally Posted by kimkats View Post
    I would test less often as you are not seeing big drops. I would say every other hour or so.

    If you add DE to your sand filter it will help clear your water faster. The only thing is that it has to be "babysat" so the pressure does not go too high. Here is a link to how to do it.

    Pool School - Add DE to a Sand Filter

    Use care when you add it as it should not be breathed in.

    Good luck! Let us know how it is going!

    Kim
    Thanks! Per your suggestion, I read up on adding DE to the sand filter. Based on everything I read, I think I am definitely going to give it a try! Waiting until tomorrow morning so I can monitor it carefully.

    6000 Gallons; Vinyl; AG; Columbia High Performance Sand Filter, 200 lb, 2 HP, 6,000 GPH; Krystal Clear SWG; 3 years old; Using TF-100 Test Kit.

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    Mod Squad kimkats's Avatar
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    Re: FC not dropping like normal during "Slam"

    For right now aim for a 30 CYA. The higher your CYA the more chlorine you will need so..............30 is just right for a SLAM. Not too high for chlorine and will buffer the chlorine from the sun.

    Have fun babysitting your pool today! It will look great when we are through with it!

    Kim
    TFP Moderator 33x52 round AG 25,600 gals Sand Filter 1.5hp Pump - 2 Speed, SLAM, Pool School, Recommended Levels, Recommended Chemicals, Pool Math, Chlorine/CYA Chart, TF-100 Test Kit

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    Re: FC not dropping like normal during "Slam"

    Quote Originally Posted by kimkats View Post
    For right now aim for a 30 CYA. The higher your CYA the more chlorine you will need so..............30 is just right for a SLAM. Not too high for chlorine and will buffer the chlorine from the sun.

    Have fun babysitting your pool today! It will look great when we are through with it!

    Kim
    My CYA is looking good!

    Have questions about adding the D.E. I followed the directions found at the TFP. 1/4 cup incremints, looking for an increase of 1 PSI. I have added a total of 2 cups of D.E. & have yet to see a PSI increase. I have been waiting & watching. I didn't want to add more until I got some advice. Thanks!

    6000 Gallons; Vinyl; AG; Columbia High Performance Sand Filter, 200 lb, 2 HP, 6,000 GPH; Krystal Clear SWG; 3 years old; Using TF-100 Test Kit.

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    Mod Squad kimkats's Avatar
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    Re: FC not dropping like normal during "Slam"

    My first question is this----------are you SURE you gauge works right? Does it drop to 0 when the pump is off? Does it ever go above your clean pressure?

    IF you are SURE your gauge works I would see what happens tomorrow with 1/4 at a time adding. 2 Cups is a lot but each pool is different. My pool likes 1 cup.

    Kim
    TFP Moderator 33x52 round AG 25,600 gals Sand Filter 1.5hp Pump - 2 Speed, SLAM, Pool School, Recommended Levels, Recommended Chemicals, Pool Math, Chlorine/CYA Chart, TF-100 Test Kit

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    Re: FC not dropping like normal during "Slam"

    I just went out & checked it again, & the PSI has gone up exactly one. Yay!!!

    Now, am I understanding right, that I need to replace the DE each time I backwash? How much of an PSI increase do you allow in your filter before you backwash?

    6000 Gallons; Vinyl; AG; Columbia High Performance Sand Filter, 200 lb, 2 HP, 6,000 GPH; Krystal Clear SWG; 3 years old; Using TF-100 Test Kit.

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    Re: FC not dropping like normal during "Slam"

    Yes, you'll need to replace the DE at each backwash. Backwash when pressure is 20-25% above clean pressure.
    ~19k Gal, IG Vinyl, Hayward SP2607X10 1hp pump, Hayward S200 Sand Filter, built in 70s, has 8 deep end with diving board, 1 skimmer, 1 return, 1 low hole, Polaris booster pump PB4-60, old Polaris robot not sure model, Rheem P-M266A-EN-C 266,000 BTU heater, solar cover, Taylor K-2006 test kit, Speedstir

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