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Thread: Chlorine level dropping fast

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    Chlorine level dropping fast

    I am new to pool ownership and still trying to figure things out. I have what's suppose to be a salt water pool, but having issues with my cell. For now I've been adding liquid chlorine to keep things going. What I am noticing is that my clorine level drops very quickly. It goes from 3.5 level to 0 in about two days. The water seems clear, I don't see any green algae. What am I doing wrong?

    pH - 7.5
    FC - 3.5 (after adding 121oz of 8.25% bleach)
    CC - 0
    AL - 70
    CH - 250
    CYA - 70
    Salt - 3200

    Thank you for your help.
    27K gal, IG pebble, Jandy JEP2.0 VS ePump, Jandy DEV60 filter, Jandy SW with ChemLink C1900, Zodiak MX8 vacuum
    The pool was repiped and new equipment installed Nov 2013.

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    Richard320's Avatar
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    Re: Chlorine level dropping fast

    1.75 FC per day is actually fairly low consumption. I see nothing wrong. Treat your pool like a pet and feed it every day.
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    Re: Chlorine level dropping fast

    What is your water temp? I've read that SWG's don't work well with cold water.
    12000 Gallon IG Plaster built 2/15/2014. Jandy 340 sg ft 127 gpm filter, Jandy 1 HP stealth pump. Circupool RJ-45 SWG (overkill). TF-100 with Speed Stir.

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    Mod Squad jblizzle's Avatar
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    Re: Chlorine level dropping fast

    Is the SWG running or not? If not, then dropping from 3.5 to 0 could be reasonable, although with the high CYA I would not think it would drop quite that much.

    You need to first figure out if there is something in the pool consuming the FC that would warrant following the SLAM Process and later figure out the SWG. To that you can Perform the Overnight Chlorine Loss Test, assuming you have one of the Recommended Test Kits.
    Jason, TFP Moderator
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    Casey's Avatar
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    Re: Chlorine level dropping fast

    3.5 - 0 with a CYA of 70 is too low of a level according to the FC/CYA chart. You should have a minimum of 5ppm chlorine and a max target of 8ppm on any given day.

    Have you performed an OCLT to see if you're losing FC at night?
    Last edited by jblizzle; 05-08-2014 at 12:03 PM. Reason: clarification
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    Re: Chlorine level dropping fast

    Thank you for all the feedback. My SWG is not running now, until the cell is replaced by Jandy. I did an overnight test a week ago and got minimal loss if any. I am using TF-100 tests. The water temperature is about 75-78F. It actually got to about 80 last week. I am in Los Angeles and we had some hot weather already.

    I guess I am comparing to the time when i lived at a condo with a pool man showing up once a week to take care of the pool.
    27K gal, IG pebble, Jandy JEP2.0 VS ePump, Jandy DEV60 filter, Jandy SW with ChemLink C1900, Zodiak MX8 vacuum
    The pool was repiped and new equipment installed Nov 2013.

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    Re: Chlorine level dropping fast

    Quote Originally Posted by Richard320 View Post
    1.75 FC per day is actually fairly low consumption. I see nothing wrong. Treat your pool like a pet and feed it every day.
    ^^^^ yup. what he said. right now im burning 2 ppm every day and we are not yet swimming. Once we start actually swimming I expect it to burn 3-4 ppm per day.
    Partially buried Doughboy Desert Spring 16 x 32, sport pool, with 7 ft deep middle, 20,000 gallons, Hayward Powerflo Matrix 1.5 HP 2 speed pump, 250 lb sandfilter, 2 Doughboy skimmers and 2 returns. 2 cascade fountains.
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    Mod Squad jblizzle's Avatar
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    Re: Chlorine level dropping fast

    FC loss is a % that is a function of your CYA level. At a 70ppm CYA, I would expect a ~40% loss in a day. Starting at 3.5ppm, there should be 2.1ppm left after 1 day and then 1.3ppm left after 2 days.

    The 2-3ppm normal loss is when you are at lower CYA levels and starting at the recommended FC levels. IF your CYA is 50ppm, you will lose about 50%. Since you start at say 6ppm, you will be at 3ppm after 1 day, and then 1.5ppm the next.

    That is why 3.5 to 0 seems off to me in this case.
    Jason, TFP Moderator
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