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Thread: Daytime chlorine loss question

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    carlos31820's Avatar
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    Daytime chlorine loss question

    I'm on day 7 of my very first SLAM in 5 years. I have a question regarding the large amounts of chlorine loss my pool experiences at these high shock levels during daytime hours. This morning, my FC was 33. When I came home from work (about 12 hours later), the FC was 25.5. However, I just realized that this morning, I had turned on my SWG at 80% and it ran all day today.

    It seems like a loss of 7.5ppm even in sunny 92 degree weather seems high - especially with the SWG running all day (I've since turned it off). However, I've never had to SLAM my pool before so I'm not familiar with these high chlorine levels and how the pool behaves.

    Does this FC loss seem right?
    16x36 Vinyl Pool - 22.5K gallons.
    Jandy Stealth 1hp pump - Jandy CS-150 filter
    Jandy Legacy 250k heater - Jandy Ei SWCG
    Jandy Watercolors LED light
    Paramount Vanquish in-floor cleaner

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    needsajet's Avatar
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    Re: Daytime chlorine loss question

    You can add your city/state/country to your profile which helps understand your conditions. Also the CYA and CC level is helpful, and description of pool before you started and what it looks like now. The FC drop is believable and suggests that your SLAM is working hard to kill algae and eliminate CC. Think about anywhere algae might be hiding (under ladder rungs, behind skimmer weir, inside light niches, etc., etc.). Keep on brushing regularly to break the biofilm protecting the algae. The faster you kill it, the faster the FC loss will slow down. The loss is also high because SLAM level exceeds the capacity of your CYA level to retain the FC. Hence the M in SLAM. The more often you Maintain it, the quicker the SLAM will go.
    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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    Texas Splash's Avatar
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    Re: Daytime chlorine loss question

    ^^ Very true. And remember Carlos, there's two things happening at once .... the higher FC level is getting expended by the abundance of organic material, but at the same time the higher FC is an easier target for the sun's UV. That's why we advise owners to not go over their SLAM level based on that CYA because even at the proper SLAM level, it will drop faster than the FC that has bonded well in an ideal ratio to the CYA. At your normal target level (with no algae) you expect to lose about 2-4 ppm each day. So you can see how losing more than that is very easy to do during a SLAM - especially just the 3.5 ppm more you experienced today. Hope that 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
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    bobodaclown's Avatar
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    Re: Daytime chlorine loss question

    Just a heads up. Use only 5ml of water then each drop counts as 1ppm. When you SLAM, you don't need the .5 accuracy.
    17K Kidney Shaped Pool Concrete (Diamond Bright) Pool, 3/4 hp 2 speed 115V Sta-rite Duraglas PEA5D-180L/P2R5D-181L (Impeller C105-92PS Diffuser C1-216P), 1.5 piping, Pentair CC100 Filter , Heat Siphon 100K BTU Heat Pump Pool Heater, Flow meter Blue White Flowmeter Model No. F-30150P, Hayward Astrolight SP0581N, SWCG CalimarTitanium Edition TE45 , Dolphin Nautilus Plus with CleverClean, Lakeland Florida

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    Mod Squad jblizzle's Avatar
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    Re: Daytime chlorine loss question

    Quote Originally Posted by bobodaclown View Post
    Just a heads up. Use only 5ml of water then each drop counts as 1ppm. When you SLAM, you don't need the .5 accuracy.
    The savings of doing this is quite minimal, just be sure to use 10ml when you go to do the OCLT.
    Jason, TFP Moderator
    18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
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    carlos31820's Avatar
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    Re: Daytime chlorine loss question

    Quote Originally Posted by needsajet View Post
    You can add your city/state/country to your profile which helps understand your conditions. Also the CYA and CC level is helpful, and description of pool before you started and what it looks like now. The FC drop is believable and suggests that your SLAM is working hard to kill algae and eliminate CC. Think about anywhere algae might be hiding (under ladder rungs, behind skimmer weir, inside light niches, etc., etc.). Keep on brushing regularly to break the biofilm protecting the algae. The faster you kill it, the faster the FC loss will slow down. The loss is also high because SLAM level exceeds the capacity of your CYA level to retain the FC. Hence the M in SLAM. The more often you Maintain it, the quicker the SLAM will go.
    Thank you for the response. I updated my profile. I live in Midland, Georgia.

    The SLAM details can be found in this post...

    SLAM questions... (and moral support))
    16x36 Vinyl Pool - 22.5K gallons.
    Jandy Stealth 1hp pump - Jandy CS-150 filter
    Jandy Legacy 250k heater - Jandy Ei SWCG
    Jandy Watercolors LED light
    Paramount Vanquish in-floor cleaner

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