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Thread: High Chlorine and CYA. Oily film.

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    High Chlorine and CYA. Oily film.

    So when I opened my pool this spring, the water was clear with a lot of dead algae on the bottom. Was covered over winter with occasional addition of 3" chlorine tabs. Pumps winterized = no circulation for 6 months. Lots of clean rainwater added.

    Vaccumed bottom with good result, which drained 25% of the water. Added tap water to normal level. Took water sample to Pool Store:
    FAC > 5
    TAC = unknown (they said they could not test it)
    pH < 7 (my pH meter read 6.7)
    TA = 100
    CYA = 80
    TDS = 500
    CA Hardness = 120

    I wanted to get the pH up first so they had me add 15lbs of soda ash. Nothing happened except a soapy/oily film developed on the surface. Skimmed off, it was greyish blue. No chlorine of any kind was added.

    Repeat testing 2 weeks later showed the only change to be in:
    TA = 130
    (pH was still <7)
    Nitrates = 10ppm
    No further advice given.

    Read the Pool School. I figured I had to stop using 3" tablets, superchorinate to get rid of the film, and aerated the water for 8 hours.

    I am using an HTH test kit that only goes to 5 on total chlorine. Through serial dilution with distilled water, I calculate the total chlorine to be 20.
    Now the water is clear, film is almost gone, and pH is "magically" up to 7.4 with no additional base added. Maybe superchlorination oxidized some organic weak acids?
    Now the previous white bottom is greyish blue (actually quite pretty) and scrubbing does nothing.
    I am concerned about the high total chlorine level and inability to measure free chlorine to guide my addition of bleach to ensure a safe pool for me and my dog (who drinks the water sometimes). I really just want to get the pool going to the point where my dog can do her physical therapy for a neurologic/orthopedic condition safely with me in the water if necessary.

    What to do?
    We are on a water meter and water is expensive here.
    When pH is low and TA is normal/high why not just add a strong base like NaOH or KOH?
    I could get a better test kit, with a wider range of chlorine measurement but am trying to save money (see below).


    Conrad Arnold
    Sacramento CA
    33,000gal, IG, circa 1970, (now) fiberglass over plaster, pac-fab paper cartridge, 1.5hp pump, polaris 280 (inoperable, UV damage) with booster, solar heat (inoperable, leak in powermat), skimmer (inoperable, line clogged & possibly fractured under concrete), main drain inoperable (long standing problem), jury rigged deep intake, skimmer line work-around in progress.
    Sacramento CA
    33,000gal, IG, circa 1970, (now) fiberglass over plaster, pac-fab paper cartridge, 1.5hp pump, polaris 280 (inoperable, UV damage) with booster, solar heat (inoperable, leak in powermat), skimmer (inoperable, line clogged & possibly fractured under concrete), main drain inoperable (long standing problem), jury rigged deep intake, skimmer line work-around in progress.

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    Mod Squad jblizzle's Avatar
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    Re: High Chlorine and CYA. Oily film.

    Welcome to TFP!!!

    Sounds like you are on your way. As you now likley realize, the FAS-DPD chlorine test would make life easier (and more accurate). What you need to realize is that the pH test will read artificially high when the FC > 10ppm ... so that is likely what you are seeing. You will need to test the pH again and adjust when the FC drops back down.

    Please add your pool details and location as described HERE as it will help us help you ... otherwise it will be lost in this single post in the future.
    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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