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Thread: Y'all have great advice! no more green water but now what...

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    Y'all have great advice! no more green water but now what...

    For a couple of weeks my water was cloudy and started turning green despite shocking with dichlor. I think I may have had mustard algae (there was a greenish-brown powdery substance on the floor--so I started shocking with liquid bleach to get the FC up. I've been scrubbing the walls and floor everyday.)

    My CYA is really high 100. (Yes, I've been using pucks and dichlor and now that it's finished I want to get going with the BBB.) And according to the CYA/CL chart I need to keep the FC at 59 with such a high CYA.

    Anyway, I've been monitoring the past couple of days and adding bleach as needed.

    Friday night
    FC=64
    CC=0
    CYA=100

    Sat. morning
    FC=59
    CC=0
    CYA=100

    Sat. midday
    FC=50.5
    CC=0
    CYA=100

    Sat. night
    FC=59
    CC=0
    CYA=100

    Sun. morning
    FC=57
    CC=0
    CYA=100

    Question 1--do I need to continue keeping the FC up now? The water cleared up yesterday morning (it isn't green anymore and no more substance on the floor) but it's still cloudy. I have had the pump on 24/7 and had the polaris running about 6hrs per day.

    Question 2--if I can let the FC level fall will the CYA start to fall as well (we're not swimming anymore)? Or do I HAVE to drain some of the water to get the CYA levels down. Not having drained the pool before, I'm assuming I'd have to rent a pump to do that and I'd rather not. When I was a kid and we had a sand filter I remember we could backwash and get rid of a lot of water that way but I've got cartridge filters now.

    Thanks!
    Devon
    20,000 gallons
    Hayward Swimclear Cartridge filter
    IG, concrete/plaster floor, gunnite sides with fiberglass over
    Waterfall, Hayward Super II pump, 2HP, Polaris 280 pool sweep w/ 3/4hp booster pump
    Built in the early 60s

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    duraleigh's Avatar
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    Apr 2007
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    Re: Y'all have great advice! no more green water but now wha

    The FC/CYA chart suggests FC of 39 for CYA of 100.......not 59. YOur FC is way too high and you need to let it drift down.

    I would then start by reading or rereading the ABC's of Pool water Chemistry up in Pool School and get a better grasp of the suggested limits on what we test for.

    Pool School will tell you that cYA of 100 is far too much to successfully manage your pool. You need to drain about 50% of your [pool or as much as it takes to get CYA down to 50

    Posting a full set of test results will get you far better help but let me answer the two questions you posed....

    1. Let your FC drift down to normal levels.....around 9 ppm for that CYA level.

    2. Draining is the only way to reduce CYA. Do it in partial steps...say 25% at a time.....until you get the desired result.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Re: Y'all have great advice! no more green water but now wha

    oops...I should have printed out the chart and not relied on memory!

    Thanks for the post. I'll see about renting a pump to drain some of the water.

    Devon
    20,000 gallons
    Hayward Swimclear Cartridge filter
    IG, concrete/plaster floor, gunnite sides with fiberglass over
    Waterfall, Hayward Super II pump, 2HP, Polaris 280 pool sweep w/ 3/4hp booster pump
    Built in the early 60s

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    Join Date
    Mar 2007
    Location
    San Rafael, CA USA
    Posts
    12,082

    Re: Y'all have great advice! no more green water but now wha

    I think he was thinking of the yellow/mustard algae shock level. It would be far better to do a partial drain/refill to get the CYA lower since you'll have to do that eventually anyway and doing it sooner will let you use less chlorine for shocking.
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
    12 Fafco solar panels; Purex Triton PowerMax 250 natural gas heater (200,000 BTU/hr output); automatic electric pool safety cover; 4-wheel pressure-side "The Pool Cleaner"

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    Re: Y'all have great advice! no more green water but now wha

    Yes, thanks for clarifying--I was shocking for mustard algae. I thought I read it needs to be in the upper 50s for that when you have such a high CYA.
    20,000 gallons
    Hayward Swimclear Cartridge filter
    IG, concrete/plaster floor, gunnite sides with fiberglass over
    Waterfall, Hayward Super II pump, 2HP, Polaris 280 pool sweep w/ 3/4hp booster pump
    Built in the early 60s

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