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Thread: Zero Chlorine reading

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    DGS's Avatar
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    Zero Chlorine reading

    Normally pool chemicals are in balance and I am normally the only person using pool 2-3 times/day 20 minutes per time. Normally shock about every 7 days.

    5 days ago big storm-lots of debris. Kept using net to clear debris and cleaned out skimmers several times-including the one on pump.

    Did a backwash and rinse.

    Everything good.

    Next day returns not working.

    Nephew came and released air from pump and returns working fine then and now.

    Nephew came out 2 days ago and brushed off algae from pool bottom.

    But today's readings on chemicals:

    Pentair Chemical Test Kit:
    Chlorine 0
    ph 7.8
    Acid Demand Had to add one drop (can I use baking soda to raise and if so how much?)
    Total Alkalinity 80ppm

    Aquacheck & test strips
    Total Hardness 250ppm
    Total Chlorine 0
    Free Chlorine 0
    ph 7.2
    Total Alkalinity 80ppm
    CYA 0

    I confess I am baffled by the chlorine reading as the dispenser is on 24/7 and always set on high and had 2 tabs still in it.
    It has been very sunny over the last 4 days and the UV has been high-but prior period of this weather didn't zero out chlorine. The algae wasn'thorrendous but there was algae on bottom (green algae)

    Any advice would help-especially what to add, how much, in what order and if to take readings in between.

    Thanks a million!
    Memphis TN New to owning a Pool.Appx. 25,000 gallon inground gunite outdoor pool appx 20x40 curvy shape surrounded by 10 large crepe myrtles and other trees.Pool was installed about 20 years ago.
    Triton II Sand Filter Pentair Chlorinator 3" tabs Polaris vacuum 3' to 7' with a diving board. Taylor 2006 FAS DPD Test Kit

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    Mod Squad JohnT's Avatar
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    Re: Zero Chlorine reading

    Welcome to TFP!

    Two issues I see. First, if you have algae it can consume chlorine rapidly. Much more rapidly than a dispenser can add it. Second, you say you have 0ppm CYA. If that is correct, sunlight will rapidly destroy the chlorine in the pool. What is your chlorine source?

    No need for baking soda. Your pH could stand to come down some, but you add muriatic acid to lower that. Adding baking soda will raise your TA, but your TA is fine where it is.

    You need to SLAM Your Pool, but you need to be sure of your CYA level to know the appropriate chlorine level.
    TFP Moderator
    20K Gallon 20X36 Vinyl Inground
    Hayward S244T Sand Filter with 1HP Whisperflo Pump. Liquidator C-201 and Solar Heat

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    Mod Squad tim5055's Avatar
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    Re: Zero Chlorine reading

    When you say "Automated Chlorine dispenser", what is that exactly? Is it using liquid or 3" tabs?
    TFP Moderator 39 X 18 23,000(ish) freeform gunite; built 2007ish; Pentair Triton II TR100 600lb Sand filter; 2 HP Pentair pump with 2.2 HP AO Smith single speed motor; 2 skimmers, 1 main drain, 4 returns w/waterfall, Stenner 45MHP2 3GPD running@ 60% - 15 gal Tank; heated by the sun CYA 200+ when I started - 50 now. Dolphin Supreme M5 Pool Cleaner. Hot Springs SX Spa, 285 gallon

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    DGS's Avatar
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    Re: Zero Chlorine reading

    3" tabs

    - - - Updated - - -

    CYA test shows zero
    Memphis TN New to owning a Pool.Appx. 25,000 gallon inground gunite outdoor pool appx 20x40 curvy shape surrounded by 10 large crepe myrtles and other trees.Pool was installed about 20 years ago.
    Triton II Sand Filter Pentair Chlorinator 3" tabs Polaris vacuum 3' to 7' with a diving board. Taylor 2006 FAS DPD Test Kit

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    Mod Squad tim5055's Avatar
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    Re: Zero Chlorine reading

    If you are using 3" tabs I do not believe the "0' CYA reading. Each tab is almost half CYA, so you really can't have zero.

    Test strips really should be called "guess strips" because the numbers they provide are closer tot aguess than reality. You have probably read it here before, but you need to order a TF100 and at least include the XL option. That will give you what you need while you are clearing the pool, and probably enough reagents for a couple of years normal use.

    The only other real option for a test kit is a Taylor K-2006. Be careful comparing prices because the K-2006 comes in sizes, designated by a letter. The basic K-2006 has .75oz bottles. You need to get the K-2006-C to get the larger bottles that you want. Even then it is a little short on the reagent & powder for the FAS/DPD test.

    I also have the SpeedStir and Sample Sizer. They speed testing and accuracy.

    Once you get an accurate test kit we can move forward as John said and SLAM the pool to get rid of what is growing.
    TFP Moderator 39 X 18 23,000(ish) freeform gunite; built 2007ish; Pentair Triton II TR100 600lb Sand filter; 2 HP Pentair pump with 2.2 HP AO Smith single speed motor; 2 skimmers, 1 main drain, 4 returns w/waterfall, Stenner 45MHP2 3GPD running@ 60% - 15 gal Tank; heated by the sun CYA 200+ when I started - 50 now. Dolphin Supreme M5 Pool Cleaner. Hot Springs SX Spa, 285 gallon

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    DGS's Avatar
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    Re: Zero Chlorine reading

    first-Thank you for your help!!!!
    I agree about the "guess strips" but when I used the Pentair first I just wanted to get a second opinion so to speak.
    I do plan to get the Taylor kit but am on a fixed income so I really need to use the Pentair for now and it seems to decently accurate. I had a highly recommended pool guy come out about 6 weeks ago and he said go ahead and use the Pentair for now and then buy the Taylor.

    Regarding the tabs-I understand the concept of the CYA in them but is it maybe possible they stopped being dispensed? Could their be a block somewhere?

    Please let me know how much shock to dispense and I will do that right now or should I wait until this evening? Pool is 25,000 gallons.

    Again-Thanks for your help!!!!
    Memphis TN New to owning a Pool.Appx. 25,000 gallon inground gunite outdoor pool appx 20x40 curvy shape surrounded by 10 large crepe myrtles and other trees.Pool was installed about 20 years ago.
    Triton II Sand Filter Pentair Chlorinator 3" tabs Polaris vacuum 3' to 7' with a diving board. Taylor 2006 FAS DPD Test Kit

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    Mod Squad tim5055's Avatar
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    Re: Zero Chlorine reading

    The point is, CYA does not go away. If you have been using tabs any CYA that went into the pool is still there unless you have changed a lot of water. The SLAM process is just that, a process that requires testing to perform. A one time addition of "shock" isn't going to fix things.
    TFP Moderator 39 X 18 23,000(ish) freeform gunite; built 2007ish; Pentair Triton II TR100 600lb Sand filter; 2 HP Pentair pump with 2.2 HP AO Smith single speed motor; 2 skimmers, 1 main drain, 4 returns w/waterfall, Stenner 45MHP2 3GPD running@ 60% - 15 gal Tank; heated by the sun CYA 200+ when I started - 50 now. Dolphin Supreme M5 Pool Cleaner. Hot Springs SX Spa, 285 gallon

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    DGS's Avatar
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    Re: Zero Chlorine reading

    Just to update-
    I id the SLAM and pool is now looking good and readings are good on chemicals and here is the primary reason why-
    The pentair chlorine dispenser elbow valve was clogged. It has now been replaced.
    Thanks again for all the help!
    Memphis TN New to owning a Pool.Appx. 25,000 gallon inground gunite outdoor pool appx 20x40 curvy shape surrounded by 10 large crepe myrtles and other trees.Pool was installed about 20 years ago.
    Triton II Sand Filter Pentair Chlorinator 3" tabs Polaris vacuum 3' to 7' with a diving board. Taylor 2006 FAS DPD Test Kit

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