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Thread: Why is my FC level higher than pool guy

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    Why is my FC level higher than pool guy

    Th guy i hired uses taylor kit with liquid Cl test while i use taylor kit with dpd Cl titration test. His FC leves ar always around 2ppm lower than my result. Thismorning for example the pool guys free chlorine test came out at 1 1/2 while my test came out at 3 1/2 can anybody help me figure out why this is happening

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    Mod Squad tim5055's Avatar
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    Re: Why is my FC level higher than pool guy

    When you say he is using the "liquid Cl test", can I assume this is the test where he fills the tube with water and puts in drops to change the color to yellow (meaning an OTO test) or is it the is the test where he fills the tube with water and puts in drops to change the color to red (meaning a DPD test)?

    Your test, the dpd Cl titration test (around here we just call it the FAS-DPD test) is the most accurate of the three. Depending on the volume of water you start with you can test to .2 or .5 accuracy with the FAS-DPD while the other tests are a "guess" at matching colors.

    So, in answer yto your question, I'm guessing the "standard" on the tube he is using has faded or he is just not good at matching the colors. With a color match test there is always going to be a larger discrepancy.

    You are using toe "gold standard" test. It is quite clear when the solution turns clear. The only real sources for error are miscounting or not holding the bottle upright and not getting uniform drops.
    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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    Patrick_B's Avatar
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    Re: Why is my FC level higher than pool guy

    Agree with Tim, and it's difficult to match a color for the same accuracy with either one of those he may be using. Let him run one with yours sometime and see what he gets. Trust your results, they are good I promise you.
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    Re: Why is my FC level higher than pool guy

    Quote Originally Posted by tim5055 View Post
    When you say he is using the "liquid Cl test", can I assume this is the test where he fills the tube with water and puts in drops to change the color to yellow (meaning an OTO test) or is it the is the test where he fills the tube with water and puts in drops to change the color to red (meaning a DPD test)?

    Your test, the dpd Cl titration test (around here we just call it the FAS-DPD test) is the most accurate of the three. Depending on the volume of water you start with you can test to .2 or .5 accuracy with the FAS-DPD while the other tests are a "guess" at matching colors.

    So, in answer yto your question, I'm guessing the "standard" on the tube he is using has faded or he is just not good at matching the colors. With a color match test there is always going to be a larger discrepancy.

    You are using toe "gold standard" test. It is quite clear when the solution turns clear. The only real sources for error are miscounting or not holding the bottle upright and not getting uniform drops.
    i meant he uses the OTO test.
    i usually perform my FAS-DPD test with 10 ml water so i get .5 ppm accuracy; i found that using 25 ml water to begin with uses up too many drops.
    thanks for your suggestions regarding his test results; i will suggest these things to him in a kind and gentle way.

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    Mod Squad woodyp's Avatar
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    Re: Why is my FC level higher than pool guy

    So................If you have your own good test kit, I'm curious to know why you've "hired a guy"?
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    Re: Why is my FC level higher than pool guy

    Quote Originally Posted by woodyp View Post
    So................If you have your own good test kit, I'm curious to know why you've "hired a guy"?
    i'm new to pool ownership, so i'm an amateur compared to the experienced pool guy recommended to me by my pool contractor. i figure it's worth watching him do things for a while before i think i'm smart enough to take over.

    he taught me to preshock before bad weather to keep up with chlorine demand.

    he found a leak at the water temperature sensor insertion point where i would have never thought to look. the leak occurred because the installation workers tightened the clamp holding the temp sensor too much and it permanently flattened the pipe and temp sensor's O-ring. the pool contractor replaced both pipe and O-ring.

    unfortunately, he didn't see that the water feature pump was way too big. a 2 1/2 hp water pump was installed instead of a much smaller pump; my pool pump is only 2 hp! the contractor's employee discovered this when they were installing the water feature, which was much later than when the equipment was installed.

    so why did i hire a pool guy? training and experience, Grasshopper.

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    Mod Squad tim5055's Avatar
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    Re: Why is my FC level higher than pool guy

    Quote Originally Posted by Marcion333 View Post
    i'm new to pool ownership, so i'm an amateur compared to the experienced pool guy recommended to me by my pool contractor. i figure it's worth watching him do things for a while before i think i'm smart enough to take over.

    he taught me to preshock before bad weather to keep up with chlorine demand.

    he found a leak at the water temperature sensor insertion point where i would have never thought to look. the leak occurred because the installation workers tightened the clamp holding the temp sensor too much and it permanently flattened the pipe and temp sensor's O-ring. the pool contractor replaced both pipe and O-ring.

    unfortunately, he didn't see that the water feature pump was way too big. a 2 1/2 hp water pump was installed instead of a much smaller pump; my pool pump is only 2 hp! the contractor's employee discovered this when they were installing the water feature, which was much later than when the equipment was installed.

    so why did i hire a pool guy? training and experience, Grasshopper.
    I can understand the feeling of not understanding when new to pool ownership, but.....

    What we teach is very different than what most pool stores and "professionals" teach. As an example, weather does not create chlorine demand. While rain may dilute the pool a little it is generally minimal - a few hundred gallons in a pool holding thousands of gallons.

    Accurate testing on a regular basis and maintaining the correct FC level negates the need to ever shock the pool.


    ************** On Edit *************

    I should have been a little clearer in my comment as I read it....

    Only two things cause chlorine demand, UV Rays of the sun (OK, or a UV light source) and organics in the water. Organics can be leaves, algae, heck almost anything living or that was living.
    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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    Mod Squad kimkats's Avatar
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    Re: Why is my FC level higher than pool guy

    You have a good test kit and US! We can/will teach you anything you need to know about taking care of a pool. It is easy and cheap the TFP way!

    Here are some great links to help you learn how to care for your pool.

    Pool School - Basic Pool Care Schedule

    Pool School - Recommended Levels

    Pool School - Recommended Pool Chemicals

    The best link of all:

    Pool School - ABCs of Pool Water Chemistry

    Let us know if you have any questions or want to check your self.

    Kim
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    Re: Why is my FC level higher than pool guy

    thanks for everyone's help!

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