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Thread: Cloudy and Algae in bottom

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    Cloudy and Algae in bottom

    For about 4 weeks now i have been batteling algae i shock it dies i vacuum on waste and in 2 days its back again i vacuumed on waste yesterday and added ph up cause thats what the pool place said i needed the as soon as i added it it went milk white and you cant see the bottom please help

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    JasonLion's Avatar
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    To shock the pool you need to bring the chlorine level up to shock level and hold it there for some time. If you let the chlorine level go right back down you haven't really killed all of the algae and it just starts growing again.

    The milky white is probably calcium but we can't really say without a full set of test numbers. Can you post a full set of test numbers, the size of your pool?
    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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    SeanB's Avatar
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    There is also a great new Shock chart by Chemgeek in the Pool School area
    sticky.php

    I know that a lot of research went into these numbers. It may be too accurate to refer to it as a "guess" chart.
    TFP Founder

    My Pool: 13K gal IG gunite with 7' spa, Pentair Cartridge Filter, Intellichlor IC40 SWG, Polaris 280 Cleaner, TF-100 Test Kit w/ salt test.

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    We need to add something at the end of the chart indicating that some minimum level of Free Chlorine (FC) is needed even at the low CYA levels -- say, 2 ppm or so -- because some reserve needs to be available in case of localized usage from oxidizing organics or breakdown from the sun. Automatic dosing systems might be able to have lower levels, but manual dosing isn't frequent enough to maintain really low FC levels. So some common sense is needed. In practice, most people have 30 ppm CYA or more in the pool so the chart is fine in that area.

    By the way, the basic rule that works pretty darn well (except for 0 ppm CYA) is that the Min FC is 7.5% of the CYA level, the Target FC is 11.5% of the CYA level, the Yellow/Mustard Min FC is 15% of the CYA level, the Shock FC is 40% of the CYA level, and the Yellow/Mustard Shock FC is 60% of the CYA level.

    Richard
    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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    JasonLion's Avatar
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    Keep in mind that many CYA tests are on the order of +-15, so it is good to err on the high side for recommended chlorine levels at the lower CYA levels. This effect is most dramatic for a CYA reading of zero, where Richards table would drastically under dose if CYA was actually 10 or 15.
    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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    Also, one will notice that the Shock column is most different from Ben's original chart. The levels in my chart are at the same disinfecting chlorine level at all CYA levels and will kill algae at the same rate. How much chlorine you really need is more a function of how much algae there is to kill and how frequently you monitor it (i.e. keep it at a high level). Technically, anything above the Min column will kill algae faster than it reproduces, but with an algae bloom the chlorine will get used up quickly and will lower the level, at least locally, below the minimum. Shock levels just get way ahead of this process and ensure enough total chlorine.

    Richard
    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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    JasonLion's Avatar
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    The way I think of the shock level is that it is the highest level that it is safe to add chlorine up to. It would be much simpler to just add chlorine up to say 100 ppm all at once instead of adding it two or three times a day, but that would cause problems so we don't. Too high a chlorine level will damage a vinyl liner and corrode metals. If it weren't for that it would be simpler to add it all at once.

    There is really a more complex optimization going on. You want to also balance the total cost of the chlorine over time. 100 ppm is wasted on regular green algea. The mustard algae level is higher because adding more at once really helps, while going to that level for green algea would be excessive. I suppose that with mustard algae you are also a little more desperate, even if you don't know it yet, so it is worth taking a little more damage risk.

    So we are trying to balance at least effective dosage, damage risk, amount of work, and measurement variability all at once.
    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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