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Thread: Can't keep chlorine in pool - HELP!!

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    Can't keep chlorine in pool - HELP!!

    I am new to the forum, but am looking for answers to my pool woes. Have an inground 42,00 gal vinyl liner pool. Had no problems until last summer when suddenly it started taking chlorine like mad. Treated for yellow algae and did ok until pool closed.

    Used a cartridge filter, but switched to sand filter this year for ease of use. Have used dichlor for 4 years with no problems in cyanuric acid until opening this year. When opened, pH was high as usual, came down as we shocked until it plummeted. Again was chewing up chlorine. 100 pounds of dichlor in first two weeks. Cyanuric level was 95, alkalinity low, chlorine hard to get a level to mainitain.

    Drained about 3 feet of water, treated with bicarb and borate and refilled, switched to calcium based chlorine. Cya down to 65, getting chlorine to stay for at least a few days. Yeah! Until it rained 5 inches. Back flushed, double shocked (no dichlor), noticed powdery precipitate at bottom of pool and again can't keep chlorine.

    Used copper based algicide in case it was mustard algae again (common in this area).

    Todays readings (at pool store): pH 7.3, free chlorine 0.6, total chlorine 1.3, copper 0.9, cya 100, alkalinity 210, hardness 200, no measurable nitrates.

    Any ideas (considering switching to salt, but don't want the expense yet, but chemicals are adding up quickly!!)?????
    27,000 Gallon IG Vinyl Pool
    with Sand Filter
    Using BBB Method

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    JasonLion's Avatar
    Join Date
    May 2007
    Silver Spring, MD

    Re: Can't keep chlorine in pool - HELP!!

    Welcome to TFP!

    The first thing you need to do is to get more reliable water testing. If you used 100 lbs of dichlor that would have raised your CYA level by 140+, from whatever it started at, which was probably already high. Yet you say CYA was 95 after that. And then you lowered CYA to 65, and yet the most recent reading is 100 again. Either you are skipping some important steps in your explanation, or your CYA tests are off significantly.

    You need to get your CYA level down well below 100 and stop using products which raise CYA. Your high CYA levels are making the chlorine ineffective, and you need to get that under control before you will be able to make any progress.

    I am also concerned about your copper level. Using copper based algaecides is risky because copper can cause unsightly stains. Your copper level is high enough to cause problems if you are not careful.

    I suggest you order a top quality test kit, and start replacing water to get your CYA and copper levels down. Then, when the test kit comes, get some reliable readings and start over from there.
    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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