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Thread: Average Chlorine Demand

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    Join Date
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    Average Chlorine Demand

    Looking to see if there is any type of average chlorine demand for a above groung pool.
    Mine seems to need 50-60 ounces per day
    Using 8.25 Fresh bleach
    CYA is 50-60 and that may be my inability to read the test just right
    PH is over 8.2
    I added 18 ounces of MA last night and the reading did not budget
    In north Texas with full hot sun
    21' NEW YORKER II 54" DEEP AGP Private Label MORADA RTR WILBAR Aluminum wall
    Hard Bottom and 1/4" Floor Pad 1/8" Wall Foam Well Water Perma 2500 Unibead liner King Technology Pool Chlorine Feeder HAYWARD Diver Dave cleaner
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    Richard320's Avatar
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    Re: Average Chlorine Demand

    Poolmath says that pool is about 10,400 gallons. 50 oz of 8.25% bleach is 3.2 FC. That's not unreasonable for full sun, especially if it gets a lot of swimmers. The way to be sure you don't have something eating the chlorine other than the sun is Pool School - Perform the Overnight FC Loss Test (OCLT)
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    Re: Average Chlorine Demand

    The steps are the only question mark in my mind as the culprit due to old sand left in them.
    The outside of them was cleaned with an ultra concentrated bleach mixed from powdered shock and a little water.
    I flushed the inside of them several times but I know there was still sand in there.

    Walls and bottom are very clean looking and feeling
    Pump runs twice per day by a timer for 6 hours each time

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    Re: Average Chlorine Demand

    You do need to get your pH down. Perhaps your TA is too high? A high pH will use more chlorine because there's a lot more hypochlorite ion and it breaks down faster. If you had around 6 ppm FC on average with 55 ppm CYA, then at a pH of 8.2 you'd have a loss of 0.25 ppm FC per hour so over 8 hours of noontime equivalent sun per day that would be 2 ppm FC. At a pH of 7.5, you'd only lose 0.06 ppm FC per hour so over 8 hours that's only 0.5 ppm FC. So just because of your higher pH you are losing around 1.5 ppm FC more than necessary.

    This estimate above is somewhat exaggerated since it doesn't account for CYA shielding, but the point is still valid. Get your pH in line and you may find that your chlorine usage drops some, more into the 2-3 ppm FC range that is more typical.
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    Re: Average Chlorine Demand

    My TA is very high around 400
    I will have time this long weekend to get some type of aeration set up to try and lower it.
    I have tested it twice and had Leslie's test it also.
    Straight tap water is over 500 unless my brand new TF100 had a bad reagent

  6. Back To Top    #6

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    Re: Average Chlorine Demand

    Make sure that you don't have static electricity on your dropper tip. You should have well-formed drops that hang until heavy and then drop. It should not squirt out. Wipe the dropper tip with a damp cloth if the drops aren't right.

    According to this Argyle Water Quality Report, your water is very, very low in calcium and the TA is only 42 ppm. So unless you are on your own well and for some reason it's flowing through limestone while other wells for Argyle's water supply are not, then I think there is something wrong with your test/testing.

    If your TA were truly that high, you would likely find your pH rising fairly quickly.
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
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    Re: Average Chlorine Demand

    This is the supply we are on http://www.swwc.com/monarch/ccr-stes-2014.pdf
    http://www.swwc.com/monarch/service-...n-county-3.pdf
    I did the test exactly like the directions said and after reporting several on the forum cautioned me to double check

    Current Readings
    PH 7.2
    FC 4.5
    CC 1
    TC 5.5
    TA 270
    Last edited by giltyler; 07-03-2015 at 07:11 PM. Reason: test
    21' NEW YORKER II 54" DEEP AGP Private Label MORADA RTR WILBAR Aluminum wall
    Hard Bottom and 1/4" Floor Pad 1/8" Wall Foam Well Water Perma 2500 Unibead liner King Technology Pool Chlorine Feeder HAYWARD Diver Dave cleaner
    Waterway 22″ Sand Filter 1.5 HP Center Discharge Pump Single speed Wide Mouth skimmer

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    Re: Average Chlorine Demand

    OK, that is completely different from what I had found. This is ground water with a VERY high TA of 471 ppm though the Total Hardness is very, very low at 3.7 ppm. Sulfates are a bit high at 82.8 ppm but not horrible. pH is high at 9.2.

    So your testing straight tap water as 500 ppm is not that far off from the 471 ppm they report so your test is accurate (remember that it is only accurate to within one drop or 10% of the reading, whichever is greater so you are well within testing error).

    So with evaporation and refill your TA will climb and you'll be adding acid to lower it and to keep the pH in check. That's just the way it will be in your pool. You can accelerate getting the TA down to try and stabilize the pH, but you will be always adding acid due to the TA rise from the fill water unless you get a pool cover to stop the evaporation.
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
    12 Fafco solar panels; Purex Triton PowerMax 250 natural gas heater (200,000 BTU/hr output); automatic electric pool safety cover; 4-wheel pressure-side "The Pool Cleaner"

  9. Back To Top    #9

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    Re: Average Chlorine Demand

    Thank you chem geek for checking the water and giving conformation that the
    TA is just going to be an issue moving forward
    I am getting it down slowly

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