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Thread: how badly am i failing OCLT test?

  1. Back To Top    #1

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    how badly am i failing OCLT test?

    The criteria for completion include FC loss of <1ppm but I haven't stumbled across anything that helps quantify how miserably one is failing the test. If I missed it somewhere, sorry.

    For the last two nights my OCLT has been between 3-4ppm. How bad is that?

    I'll admit, I'm being kind of a lazy SLAM, more of a slap or an evil stare. This is the case because I work all day and there has never been any green. i only started to SLAM because I got bored/curious and ran an OFCL test while getting reacquainted with my TF-100. I've been doing it for 4 days with no change.

    The pool has only been setup for 3 weeks. Since the moment I got over 75% filled I started adding granular dichlor to raise both FC and CYA till I ran out. Then started adding 3" trichlor pucks to continue the process. I don't think FC has ever been below Min for the estimated amount of CYA I had. Perhaps I was wrong.

    I am fairly certain that the three things I'm doing wrong with both SLAM and OCLT test are 1) only testing early morning and after the sun goes down, 2) I probably need to target night time FC level so that next morning is still at shock level 3) I've been turning off my pump overnight rather than being smart and letting it run with both copper and salt cell unplugged. I do leave the pump on, cell working, and trichlor puck in the skimmer basket during the day while at work.

    Last two nights went like this:

    Monday night - FC = 12

    Tuesday morning - FC = 9
    <Tuesday-day = ran SWG 5 hours - about 1/2 8oz trichlor puck dissolved>
    Tuesday night = FC = 12.5

    Wednesday morning - FC = 8
    <today SWG on 12 hours - probably another 1/2 8oz puck will dissolve>


    Other #'s
    CC was 1 the other day, been .5 since.
    Ph 7.8 [edited]
    TA 80
    CH 120
    CYA - 25 tested, 35 calculated via Pool Calculator (since i'm still adding, figure it won't show up in test for a week)
    Borates = 50ppm
    Salt 3,2xx

    Does anyone have any further suggestion, or prodding? Do you think that if I just kick up the chlorine a bit more, like 16ppm, and run the pump all the time that it'll clear up pretty quickly?

    Below are two pics. I don't know if they qualify as dull or not. Of course pics are difficult evaluate from.
    Attached Images Attached Images
    Intex UltraFrame 14'x48in - 3,900 gallons. Intex 1600 GPH combo Sand Filter/SWG Hard Plumbed w/Hayward skimmer, suction & return. Borates.
    And... 15k gallon kidney shaped gunite 1975 vintage. Hayward DE3620 filter + Hayward 750 pump.
    TF100 Test Kit | Pool School | Pool Math

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    Mod Squad jblizzle's Avatar
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    Re: how badly am i failing OFCL test?

    It is a little more tricky with a SWG. Ideally you would turn the SWG off in the evening and leave the pump running and test at least an hour after chlorine was added (SWG turned off). Then in the morning you need to test before the sun come up.

    I am wondering if you are not getting a good reading on the FC in the evening due to the SWG on and then getting a bad reading in the morning because you have not been running the pump over night.

    BTW, you need to get your pH up as all the pucks and dichlor have driven it too low.
    Jason, TFP Moderator
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  3. Back To Top    #3

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    Re: how badly am i failing OFCL test?

    Thanks Jason. Oops, typo there on the Ph. It's 7.8, a bit higher than it was before I did borates this weekend.

    Good point on the possible reading flaws. This evening I'll yank the puck out of the skimmer, unplug the cell, wait 1-2 hours THEN take my evening test. Leave the pump on through the night (cell still unplugged) and see what i get in the morning. I'm hoping this is the case. As nice as the water looks overall, i can't believe it seems so hard to pass this test. Yes, I know there can be not-yet-visible algae being barely contained by the chlorine load... I would simply be surprised I'm there.
    Intex UltraFrame 14'x48in - 3,900 gallons. Intex 1600 GPH combo Sand Filter/SWG Hard Plumbed w/Hayward skimmer, suction & return. Borates.
    And... 15k gallon kidney shaped gunite 1975 vintage. Hayward DE3620 filter + Hayward 750 pump.
    TF100 Test Kit | Pool School | Pool Math

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    Re: how badly am i failing OCLT test?

    Quote Originally Posted by hyperionguy
    CYA - 25 tested, 35 calculated via Pool Calculator (since i'm still adding, figure it won't show up in test for a week)
    If you've calculated CYA for 35, I would treat it as 40 and shock to 16 then do the OCLT from there.
    12500 gallons, 24 foot round above ground
    Hayward Sand filter, Pentair OptiFlo 1HP 2-Speed pump

  5. Back To Top    #5

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    Re: how badly am i failing OCLT test?

    Repeated last night and got the same results.

    After running SWG all day and adding some bleach mid-day, came home from work and unplugged cell after there was no direct sun (5:30). I ran the pump another 1.5 hours then tested FC. It was at 23.5.

    I left the pump running all night with the cell unplugged. At 6:45 this morning it was 19.5.

    Interesting thing is that I tested twice this morning. Once with my normal heaping spoon of DPD powder. That reading gave me 18 ppm. Dumped, rinsed, retested with two heaping spoons and got the 19.5 reading. So either my DPD is getting stale after a year or I don't know what I'm doing.

    I added bleach to get me up to 22ppm and plugged the cell in. I left it set to run all day. It will usually at least maintain that level this time of year (98-100 degree air, 88 degree water, always 1/3 shaded by 11' cantilevered umbrella).

    Water is crystal clear, at least.

    1 or 2 more days and I'll assume I'm just not testing right and let it drop down to normal levels I can test with the OTO and see if it shows a big drop at the lower levels too.
    Intex UltraFrame 14'x48in - 3,900 gallons. Intex 1600 GPH combo Sand Filter/SWG Hard Plumbed w/Hayward skimmer, suction & return. Borates.
    And... 15k gallon kidney shaped gunite 1975 vintage. Hayward DE3620 filter + Hayward 750 pump.
    TF100 Test Kit | Pool School | Pool Math

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    Re: how badly am i failing OCLT test?

    1. Test results - make sure you are taking the FAS/DPD test to endpoint each time. That involves adding drops until the very last drop produces absolutely no further color change. Subtract that drop and that is your test result.

    2. For our purposes, there are only 2 things that consume chlorine....organics in your pool and sunlight. The purpose of the OCLT is to eliminate sunlight so you are then left with a pretty inescapable conclusion.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Re: how badly am i failing OCLT test?

    Quote Originally Posted by duraleigh
    The purpose of the OCLT is to eliminate sunlight so you are then left with a pretty inescapable conclusion.
    Reading his post he seems to have done his night time test at 7PM which seems early. What are the effects of direct sunlight vs no direct sunlight? I would think it would be more appropriate to wait until sun is set?
    12500 gallons, 24 foot round above ground
    Hayward Sand filter, Pentair OptiFlo 1HP 2-Speed pump

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    Mod Squad zea3's Avatar
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    Re: how badly am i failing OCLT test?

    5:30 is way too early to start the OCLT test in August for Houston. As long as there is sunlight hitting the pool there will be chlorine lost to UV exposure. A good rule of thumb is if you don't need headlights to drive, it is the wrong time to do the OCLT. Wait until dusk, almost full dark to run the first test and do your morning test at dawn before the sun is fully up.
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    Re: how badly am i failing OCLT test?

    Oh, I figured no direct sunlight was ok, but it make sense. Will adjust tonight.

    Also, i think that until last night my FC at dark was too close to shock level for my calculated CYA level and was probably falling just below shock shortly after dark. So last night i bumped it up to shock level for 20% higher than calculated CYA. Plan to do that again tonight. Like I mentioned earlier, I bumped to 22ppm this morning and left cell running all day, so i won't fall behind during the heat/sun of the day.

    Thanks for the reinforcement, folks.
    Intex UltraFrame 14'x48in - 3,900 gallons. Intex 1600 GPH combo Sand Filter/SWG Hard Plumbed w/Hayward skimmer, suction & return. Borates.
    And... 15k gallon kidney shaped gunite 1975 vintage. Hayward DE3620 filter + Hayward 750 pump.
    TF100 Test Kit | Pool School | Pool Math

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    Re: how badly am i failing OCLT test?

    I'm a little late in my updates. I was trying to both SLAM and increase my CYA and I decided to stop trying to multi-task and have only one variable - chlorine-.

    So I recalculated what CYA should be, which was easy since I used Excel to track everything added to the pool since the fill. I calculated 50, so shock level is 20. I looked back at my daytime and overnight average consumption and added that to my shock level so that while at work and overnight I would never get below shock level. It mostly worked. I kept raising to 24ppm using just bleach and the low point was always between 18.5 - 20.

    I'm in the clear now, and I'm running the SWG enough to gently drift the FC down. It's at 14 now. Happy Days!

    Thanks!
    Intex UltraFrame 14'x48in - 3,900 gallons. Intex 1600 GPH combo Sand Filter/SWG Hard Plumbed w/Hayward skimmer, suction & return. Borates.
    And... 15k gallon kidney shaped gunite 1975 vintage. Hayward DE3620 filter + Hayward 750 pump.
    TF100 Test Kit | Pool School | Pool Math

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    Re: how badly am i failing OCLT test?

    Excellent work!
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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