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Thread: Chlorine Use for 33K Pool

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    Chlorine Use for 33K Pool

    This is the second season I am caring for our 33K inground, vinyl pool. The pool has a west exposure and is in the sun from 10 AM till sundown. We have a lot of hot, sunny days days here in Missouri. The latest water readings this morning were FC-3, CC-0, TA-80, pH-7.6, and CYA-55. These have been typical the past 2 weeks. I plan to raise FC to 6 or even higher if I bring up the CYA level. I haven't tested FC overnight drop for awhile, but it was 0 the last time I checked. Last year, the use of dichlor and trichlor brought the CYA level well over 100 by mid summer. When I learned about the BBB method, I converted to bleach and luckily didn't have any problems the rest of the summer. When I closed the pool in September, CYA levels were still way over 100, but when I opened in early May, CYA was well below 30 (the Taylor black dot tube was almost clear; used new reagents). Where did all the CYA go? Last year I could hold FC levels by adding 3 quarts of 6% per day. This year it is taking 1.4 gal. to hold FC. Is this reasonable or should I keep raising the CYA level up to 80 as suggested for high sun pools? I would like to keep CYA as low as possible, but my current chlorine use is running about $100 per month. But then again, there's a lot of water out there. Thanks for your help.

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    duraleigh's Avatar
    Join Date
    Apr 2007
    Sebring, Florida

    Re: Chlorine Use for 33K Pool

    We have all noticed that CYA has a bad habit of disappearing over the winter in many pools (mine included). It usually seems associated with pools that are not close (allowed to get pretty dirty...mine included )

    Regardless, I would immediately bring CYA up to 50-60 and see how your consumption goes. If it's still excessive, you might consider a little higher but I get kinda' squeamish suggesting much over 60 in a manually chlorinated pool.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    In the Industry

    Join Date
    Feb 2012
    Phoenix, AZ

    Re: Chlorine Use for 33K Pool

    Quote Originally Posted by philirene
    FC-3, CC-0, TA-80, pH-7.6, and CYA-55
    I understand that your CYA is already 55. Am I correct? If so, I personally would not raise it anymore. Do you use the pool often? A high bather load will also contribute to chlorine consumption.

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    Join Date
    Oct 2011

    Re: Chlorine Use for 33K Pool

    Dave, I have not had a large pool long enough to know the trends (had a smaller Intex pool that was drained every year, and I simply used bleach and didn't even worry about stabilizer). Does your CYA level drop every winter consistently? I am in Minnesota, and if I know the CYA would drop every winter, I would consider use some tri-chlor pucks for most of the summer and not deal with as much bleach. I am not sure how much my CYA will drop during the normal water replacement from winterizing.
    20x44 IG vinyl. Intelliflo, Pentair Cartridge Filter (420ft^2), Raypac 336K, Kreepy Krauly

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    Re: Chlorine Use for 33K Pool

    I have only opened the pool twice and both times the CYA was below 25 and probably much lower. Had I known that my bleach consumption was going to be so high, I would have considered trichlor pucks to maintain FC and also get stabilizer levels around 55 where I am now. Then I could have switched over to bleach, although the consumption rate would still be high at that point. If the CYA level is really low again at next year's opening, after shocking I might consider using trichlor early until stabilizer levels are around 50 and then return to bleach. Does this sound like a decent plan or am I missing something?

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    Re: Chlorine Use for 33K Pool

    Yes, the CYA level is already 55. The pool gets light use, 1-2 people during the week and 5-10 people on weekends. It seems to me that I'm losing most of the FC to sunlight.

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    Richard320's Avatar
    Join Date
    Jan 2010
    San Dimas, CA (LA County)

    Re: Chlorine Use for 33K Pool

    Sounds fine. The source of your chemicals is not important, as long as you know what you're adding and why.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
    A pool is like a pet - you have to feed it every day, even the days you don't want to play with it!

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