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Thread: Chlorine Consumption and SLAM question

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    Join Date
    Jul 2016

    Chlorine Consumption and SLAM question

    So I run a 22,000 SWG inground plaster pool with a DE filter and in SE PA, US. Current temp on pool is around 87F w/o heater on. I have found the forums here extremely helpful and LOTS of useful information. I am a chemist by training, so unerstanding all aspects of pool chemistry are relatively easily and have read pool school. Did have some green alge growth and a bunch of 9 year olds at a pool party 2 weeks ago, although Phos is only 300. I have been having trouble with FC levels, have followed SLAM guidelines CYA of 60 everything else balanced. Issue is I have low drop overnight, 1 PPM, but 8 hours later down to under 0.5 PPM. Pool is crystal clear, but still unable to hold a FC level anywhere near normal. Going on the 3rd night of reaching 30 PPM FC with liquid Cl, 10%. Any thoughts on my issue? Pool is only 2 years old, so could it be the cell in a Nature 2 system? Perplexed and frustrated at the issue. Want some insight before I make an investment into a new cell. Continue SLAM? Unfortunately can't be home during the day to monitor FC levels.

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    needsajet's Avatar
    Join Date
    Jan 2016
    Sydney, NSW, Australia

    Re: Chlorine Consumption and SLAM question

    Welcome to TFP! Good to have you here

    What was your pH before starting the SLAM?

    Nature 2 has copper, silver and either a chlorine puck feeder or an SWG. Turn it off while you get the SLAM done and we can talk about it later. If it's the puck feeder type, let us know.

    If you're pretty confident about your 60 ppm CYA, then shock level for the SLAM is 24 ppm FC. When you're at shock level, FC is burned off by the sun more quickly because it's overwhelming CYA's ability to hold it in reserve and protect it. At 30 ppm FC, that effect is even more pronounced. That said though, the FC is mostly just doing its job and killing algae. By the time you see algae with the naked eye, it's already a substantial population, it's reproducing quickly, and it all needs to get killed off.

    To speed it up, MMMaintain at shock level and brush regularly. Try to find any hidden algae farms (e.g. behind skimmer weird, under ladder rungs, inside light niches, under coping overhang, inside wedding cake steps, etc.

    To get the best advice here, take a minute and click "Read before posting" in my signature. It has instructions for adding your pool details as a signature, which will help you get the best possible advice here.
    12k IG salt; glass beads in plaster; K-2006C, K-1766 Salt, CCL, and Aussie 4in1 (HTH); Pentair Eco800 VS; Zodiac SWC 1.3 lb/day (25 g/hr); 25" filter recycled glass; OKU solar panels; 1/2 HP solar pump; Pentair Rebel pool cleaner; FlowViz flow meter; prior pool AG 10k - Be Safe - FC / CYA Chart - Become a TFP Supporter - Read Before Posting

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