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Thread: Confusing FC levels and algae

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    Confusing FC levels and algae

    Ok, have been testing with the TF-100 and thought all was good, however the pool has gone cloudy and greenish again, even with what I think are reasonable FC levels.
    Current test:
    FC: 8.5 (added CL last night), just prior to that was 7.0, day before 5.5.
    CYA: 60
    CH:390
    This seems to be a roller coaster ride, just when it seems like its under control, it goes green/cloudy again. Could the high CH level have anything to do with it? It's not cloudy all the time, just when it goes off the rails.
    This is bloody frustrating, I seem to spend 10 times as much time looking after the pool as actually enjoying it.
    I think I am going to switch to SWG, and get a Great White Shark floor cleaner. I've got so much other stuff to do in my available time (renovating, what joy...) that I don't need to be wasting time and money chasing this pool around in circles. Any advice?
    41k litre (11k gal) shotcrete in ground pool, Hayward super 2, Davey Monarch 28, zodiac SWCG
    - undergoing a transformation!
    2nd season Pool Owner. TF-100 testing
    Melbourne, Australia.

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    JasonLion's Avatar
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    Re: Confusing FC levels and algae

    Could you post the rest of your levels, especially PH and TA?
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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    Re: Confusing FC levels and algae

    Yep. pH is 7.4, TA 110, pool temp 25 deg.C
    41k litre (11k gal) shotcrete in ground pool, Hayward super 2, Davey Monarch 28, zodiac SWCG
    - undergoing a transformation!
    2nd season Pool Owner. TF-100 testing
    Melbourne, Australia.

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    Mod Squad jblizzle's Avatar
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    Re: Confusing FC levels and algae

    I can not remember if you have already gone through the shock process or not.

    If so, are you sure you passed the 3 tests before you stopped? If you do not pass the OCLT, then that shows that there is something still living in the water which can then start to grow when the FC levels lowered.
    Jason, TFP Moderator
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    Re: Confusing FC levels and algae

    I had shocked it a week ago or so, overnight loss less than 1 ppm on Saturday, CC has been 0.5 for the past few tests, and the water was clear. Yesterday it was not quite as clear, so I gave it more Cl last night. This morning it was slightly green, not on the walls, just the cloudy shade of the water. I have vacuumed the floor this morning as well, back washed, rinsed, returned to filter and now you can barely see the bottom at the deep end. Maybe I should be vacuuming to waste again, and topping up to reduce the CH?
    41k litre (11k gal) shotcrete in ground pool, Hayward super 2, Davey Monarch 28, zodiac SWCG
    - undergoing a transformation!
    2nd season Pool Owner. TF-100 testing
    Melbourne, Australia.

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    Mod Squad jblizzle's Avatar
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    Re: Confusing FC levels and algae

    Try the OCLT again to see if that confirms an organic problem.
    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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    Re: Confusing FC levels and algae

    OK. Yesterday, after everyone had finished with the pool (it's been busy, 9 days over 30deg. C), I checked chlorine.

    FC level 7.0.

    I added some and let it circulate for 3 hrs and retested.

    FC level 8.5
    CC level 0.5

    Left it overnight, retested this morning

    FC level 7.5

    Retested this evening

    FC level 5.5
    CC level 0.5


    Pool is looking greenish, but I think mostly from stuff on the floor. Haven't had time to vacuum it yet. Water is fairly clear, but not sparkling.
    I think the simplest answer is to vacuum to waste, top up, shock and let it sort itself out, nless anyone recommends otherwis.
    Removing the water will help reduce both CH and CYA, both of which are at higher levels than I want.
    I'll let you know how I go.
    41k litre (11k gal) shotcrete in ground pool, Hayward super 2, Davey Monarch 28, zodiac SWCG
    - undergoing a transformation!
    2nd season Pool Owner. TF-100 testing
    Melbourne, Australia.

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    Mod Squad Bama Rambler's Avatar
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    Re: Confusing FC levels and algae

    That sounds like a solid plan. The fact that you have .5 CC's, lost 1 ppm FC overnight, and looks "greenish" would make me want to hold the pool at shock level for a day or two and then run the OCLT again.
    Dave J. TFP Moderator
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    Re: Confusing FC levels and algae

    Ok, brushed the walls and floor today and the water is very cloudy and green, definitely algae, although none is sticking so must be dead. Last night I hit it with Cl, about 2 1/2 cups of Cal Hypo, but didn't test it again. Tonight, tested FC at 9, added 13% bleach, circulated an hour or so, FC up to 18, added another 2L bleach and its now at 24. I'm going to hold that for a few days, then vacuum to waste, top up, balance back to FC of around 7 and see what happens. I dare say our swimming season is soon to be over, so now I have to learn what to do for winter. At least it doesn't get below freezing here...
    41k litre (11k gal) shotcrete in ground pool, Hayward super 2, Davey Monarch 28, zodiac SWCG
    - undergoing a transformation!
    2nd season Pool Owner. TF-100 testing
    Melbourne, Australia.

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    Re: Confusing FC levels and algae

    Looking better today. Water much clearer, much less green thanks to high FC and filter 24 hrs. Ran a full set of tests just now:
    FC: 19 (was 24 last night, but within an hour of adding bleach)
    CC: 0.5 (seems to be the norm now)
    pH: 7.3-7.4
    TA: 100
    CH: 400
    CYA: 60
    So it looks like the CYA and CH are still a bit high, a vacuum and top up will help both. I want pH around 7.2 as I find the Cl works better there and the FC up around 20 still so more bleach to go.
    For what it's worth, the tap water here has a CH of 40, pH of 7.2 and FC of less than 0.5. On the way there, though.
    41k litre (11k gal) shotcrete in ground pool, Hayward super 2, Davey Monarch 28, zodiac SWCG
    - undergoing a transformation!
    2nd season Pool Owner. TF-100 testing
    Melbourne, Australia.

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    Re: Confusing FC levels and algae

    I feel your pain. Last year towards the end of summer I had a slight outbreak but nothing ever got really green, just cloudy. I think I had to keep the chlorine level at shock level for over a week before whatever had control of my pool died.

    I tested and tested and put bleach, lots of bleach in, but it just seemed that it wasn't working. That's when I learned about heat and bleach. Once I got new bleach and kept in reasonable cool and out of the sun, things started clearing up better.

    I had never really brushed much before that outbreak because I really never needed to. Brushing really helped get the job done.

    I will be interested how all this works out, keep us up to date if you can.

    Bob E.

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    Re: Confusing FC levels and algae

    Yep, brushing the sides and floor every day now and whatever is in there, the quantity is reducing. The water is very clear right now, and with less sediment on the floor so I'll keep the 20+ FC level for another day or so, maybe even do the OCLT tonight to see how it's going. At the moment it's cold and raining so no swimming anyway.
    Great weather for the Grand Prix...
    41k litre (11k gal) shotcrete in ground pool, Hayward super 2, Davey Monarch 28, zodiac SWCG
    - undergoing a transformation!
    2nd season Pool Owner. TF-100 testing
    Melbourne, Australia.

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