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Thread: SWG Size. What output to expect?

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    Join Date
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    SWG Size. What output to expect?

    I love this forum!! Thank you.

    I bought an 18x36, in ground, 22,500 gallon vinyl pool in fall of 2004. For the Fall "deal" I got a free Zodiac Clearwater LM2-15 SWG.

    After last summer, and now this summer, struggling with algae, I got fed up and took matters into my own hands and educated myself on this forum and the old Poolforum.com. Now, I am not at the mercy of the pool store sales people any more. Thank you to all you regular problem solving contibutors!!

    I've had my water tested every day for a week now (after draining half the water, since CYA was at +150). Using a lot of bleach, the algae is gone and pool looks good. (I added 20 Mule Team also, to 30ppm). The problem is that I cannot get the TC and FC up, or CC to zero, running pump and SWG 24/7. I've hit the super clorinate button 3 days in a row now. CYA read 90 yesterday. Salt at around 4,000. TC stays around 1 or less.

    So last night, I looked to see what model of SWG was give as the "fall special" (see above), and I searched the internet to see what I could find. Looks like my model is good for 60,000 liters max, or 15,850 gallons. My "free" SWG should have been the LM2-24 for my size pool.

    TWO QUESTIONS:
    1. How long should I have to run my pump and SWG (at what level), to keep FC at 3-5ppm?
    2. Given that my pool was installed 2.75 years ago, what should I expect from the pool store where I bought it?

    Thanks everyone!
    22,500 Gallons
    18x36 Feet Vinyl
    Zodiac Clearwater LM3-24 SWG

  2. Back To Top    #2
    JasonLion's Avatar
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    You should not expect even a over sized SWG to kill algae once the algae has gotten started. To kill algae you want the FC level to go up very quickly, which no SWG is capable of doing. You should start shocking the pool with bleach and suppliment it with the SWG. You need the initial "shock" of the bleach addition to get enough ahead of the algae to kill it off.

    Test the water and add bleach to shock level (from Ben's best guess chart) twice a day while running the SWG. The SWG will help with chlorine addition between the times you can be there and the whole process should go more quickly than with bleach alone.

    Once the algae is gone you can figure out what a proper run time for the pump/SWG is.
    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

  3. Back To Top    #3

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    NW Arkansas
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    Thanks, JasonLion,

    I think that I have gotten past the algae now. I drained half the pool (to reduce CYA from 150ppm), and shocked the daylights out of it for a few days. Pools seems increasingly clear, and no tint of green.

    So now, I do want to understand what to expect from my SWG. From other posts, it sounds like I shouldn't have to use bleach any more, except perhaps after a rain or heavy use. SHOULD a right sized SWG be able to maintain 4-5ppm TC being run 8 hours a day at 60%, or ???.

    My electric bill in the summer, between air conditioning and 24/7 pool pump will push $500/mth! So, you can see that I'm looking to find out how to minimize costs. I hope to understand what to expect from my SWG. I've come to the conclusion that my pool store, where I bought my pool, is of minimal to no help. This morning I asked one of the sales guys to check into my model, and see if it will support 22.500 gallons. Will they give an honest answer, if they come to realize that it is not the correct size? Will I know if it's honest?

    BTW, my test from the store yesterday and today are as follows:

    6/29 (6:30 AM sample kept in trunk of car for 4 hours b/4 test) Pushed "super clorinate" at 5:30pm previous eve.
    TC 0.9
    FC 0.7
    CC 0.2
    CYA 90
    pH 7.3
    Salt 4,500 ppm

    6/30 (8:00 AM sample, direct to store for test) Pushed "super clorinate" at 5:30pm previous evening
    TC 1.5
    FC 1.2
    CC 0.3
    CYA 93
    pH 7.4

    (I do have a Taylor 2006 test kit on order, but it still hasn't come. Wish I had known about the kits advertised on this sight first.)
    22,500 Gallons
    18x36 Feet Vinyl
    Zodiac Clearwater LM3-24 SWG

  4. Back To Top    #4

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    NW Arkansas
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    I called Zodiac and confirmed. The LM2-15 is rated for a 15,000 gallon pool max. (I'll wait until Tuesday, when the "guy who knows" at my pool store will be in to answer the question as to max rating and why they installed the -15 instead of the -24.)

    I can upgrade/convert under my 3 year prorated warrantee to the LM3-24 for $383. That's the cell only, since the same generator/power pak can be used.

    Do you think my pool installer will cover the converstion to the next model up? Should they?

    If not, would it be worth the money to upgrade out of my own pocket? Or should I live with a "hybrid" part SWG-part manual bleach addition?

    All advice and comments welcome!
    22,500 Gallons
    18x36 Feet Vinyl
    Zodiac Clearwater LM3-24 SWG

  5. Back To Top    #5
    JasonLion's Avatar
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    May 2007
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    Silver Spring, MD
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    The general rule for SWG sizing is that they are sized assuming 24 hour a day run time on the hottest day with the highest bather load. Under ordinary summer conditions they can usually run for as low as half that long on a max sized pool. Of course different manufacturers make a judgement about what a worst case day is in different ways.

    Given your unit is undersized, running your system 24/7 should still generate enough chlorine if you don't have a high bather load or a heat wave.
    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

  6. Back To Top    #6

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    Location
    NW Arkansas
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    I'm going to continue this on the new topic "SWG and Nature2"
    22,500 Gallons
    18x36 Feet Vinyl
    Zodiac Clearwater LM3-24 SWG

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