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Thread: Slaming pool, what is shock FC?

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    Slaming pool, what is shock FC?

    Sorry for my lack of knowledge but I am planning to slam the pool and just want to make sure I do this right.

    here is my pool data
    FC 0
    PH 7.8
    TA 90
    CYA 80
    Borates 80

    Water is clear but I am loosing lots of chlorine so I know I need to slam it and bring my FC to 8 or 9. I am looking at the chart but not sure what is shock FC 31 stands for. I have taylor K2006 but not sure if there is a test for shock FC. Do I need to be concern with this? TIA.
    Last edited by sangweb; 05-02-2014 at 07:50 AM. Reason: mispelled

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    Richard320's Avatar
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    Re: Slaming pool, what is shock FC?

    Shock FC is the level you need to maintain to kill the algae off faster than it can reproduce. It's really high because you have such high CYA. 8 or 9 would be the maintenance level for FC.

    To SLAM means to hit the algae really hard and then hit it again and again and again before it can recover. Knock it down and kick it until it's dead, never let it catch its breath. SLAM is an acronym for Shock Level and Maintain. Pool stores will teach you to shock once. You might win the battle, but you won't win the war. You need to keep it up again and again, every couple hours.

    Time to reread SLAM instructions.

    With your high CYA level, most people here would advocate draining and replacing some water before you SLAM, but if it's clear, you might be able to get ahead of the algae before the pool turns cloudy if you start now. Once it is clear, you will need to ensure the FC level never gets below 6, which precludes using that little color-matching FC test ever. So order some powder refills now, you'll be using the FAS-DPD test every day.
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    Re: Slaming pool, what is shock FC?

    Shock FC 31 just means 31ppm Free Chlorine. It's the same test as the standard chlorine test - you are just testing for 31ppm instead of 8 or 9 ppm.
    22,000 gallon in-ground kidney-ish shape: 1 HP pump and Triton TR60 sand filter. NEW: Dolphin Nautilus robot! :)

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    Isaac-1's Avatar
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    Re: Slaming pool, what is shock FC?

    To put it another way FC is Free Chlorine, your shock goal level appears to be 31 ppm which I assume you based on the CYA Chlorine chart in pool school for a CYA level of 80 ppm. To SLAM your pool you must maintain a shock level of 31 ppm FC. during normal maintenance you would need to maintain a level of 9 ppm, these are both due to your high CYA level which is mediating much of the effect of the FC in your pool. This is a prime example of why we suggest a CYA level in the 40 ppm range for most pools, at 80 ppm CYA you are at w point that it takes an insane amount of chlorine to clear up any type of algae bloom, and your maintenance levels are high enough that even managing that becomes difficult, at a CYA level of around 90-100 we feel that this becomes nearly impossible if there is algae present and water replacement prior to shocking becomes the only viable option. As you can see you are approaching that point, and while partial water replacement to lower CYA may not be necessary in your case, it might make life a lot easier.

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    Casey's Avatar
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    Re: Slaming pool, what is shock FC?

    Are you running a SWG? Please update your signature with your pool specs and tell us what you have to play with.

    If you don't have a SWG you should really do a partial drain refill and retest CYA.
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    Re: Slaming pool, what is shock FC?

    Thank-you for all the responses, looks like I am going to have to drain the pool this weekend. The funny thing is I've just drained about 1/3 of it just last month to prepare for the summer and I finally had it with with shocking weekly because green spots kept popup every week. I've finally join the TFP to decided to handle the matter myself. I've bought a Taylor Test Kit and borated the pool and I've never tested for CYA until the kit arrived and started noticing the lost of Chlorine. The water seems to be clear after borated, no algae, just weekly test of Chlorine appear that all are gone. I am in Houston TX so water here evaporate pretty quick so I was hoping not to drain the pool again and Slam it until the CYA get lower to ideal.
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    Isaac-1's Avatar
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    Re: Slaming pool, what is shock FC?

    I think that is probably a good idea, even another 1/3 drain and refill will make things much better, being in Houston in the sunbelt you may want to aim for a goal of 50 ppm for CYA
    Indoor 20x40 35,000 gallon vinyl pool with 1.5 HP 2 speed Jandy FloPro pump, Hayward EC75 Perflex DE filter, 11 4x12 Techno-Solis solar panels w/ Aquasolar controller, Aquabot Turbo T Robot Cleaner. Also LMI metering chlorine dispenser pump and HotSpring Jetsetter
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