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Thread: Me vs. The Pool Guy

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    michaelrbanks's Avatar
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    Me vs. The Pool Guy

    I had an interesting opportunity yesterday. The pool builder sent out a tech for routine service under the first year protection plan & I got to watch him test my water. He was packing a Taylor K-2006 & knew how to use it. All the parameters for pH, TA and CYA matched mine perfectly, but the FC was off. We both used the DPD method of testing FC.

    At 6:00 a.m. that morning, I tested and added enough bleach to bring it up to 5.5 PPM.
    Pool Guy showed up and tested around 3:00 p.m. after the pool baked in the sun, so I expected some loss. He got 3.0 PPM.
    I did not do anything after he left until 6:00 a.m. today. When I tested this morning, I got 4.0 PPM

    So where did the extra chlorine come from?

    Some notable differences between how we tested: I test early in the morning at the deep end, pulling water from probably 6-8" below the surface. Pool Guy tested in the blistering afternoon sun in the shallow end. I did not notice how deep he sampled.

    Could there really be a 1 PPM difference within my pool, based on sample location?
    16,661 gal IG PebbleTec w/ Spa; 60 ft2 Jandy DE filter, 2 HP Jandy Variable Speed pump; 2 skimmer; 400K BTU Jandy heater; Polaris Sport; opened 9/15/14; TF-100 test kit

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    Texas Splash's Avatar
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    Re: Me vs. The Pool Guy

    Yes, those difference can/do make a differences in your results. Some people don't think too much about it for normal everyday testing of FC, but you can best when it comes to an OCLT where 1ppm means the difference between a SLAM or not, you test like a robot and standardize everything you do. At least you are experienced and now.
    Pat (a.k.a. Texas Splash) ~ My Pool: Viking Fiberglass; 17,888 Gal; Waterway Supreme 2-sp/2-hp pump; Hayward Ctg filter; TF-100 w/ Speed Stir
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    Re: Me vs. The Pool Guy

    Also, which test volume did he use versus you? Small variations in actual sampled volume can lead to different ppm. Also, variations in the amount/age of powder might contribute to ppm differences.
    Bob - Palm Beach by San Juan Pools. approx 5000 gals., Pentair 320 cartridge filter (all new guts installed by me), Goldline SWG, 'New to me' Kreepy Krauly Sand Shark, Intermec 104 Timer Test kit: TF-100 w/Speed Stir

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    Re: Me vs. The Pool Guy

    if the water's not circulating, the water at the top would have a lower FC due to higher sun UV exposure. And, if your water isn't circulating, that's probably the better reading to have, as it shows where the weak point in your water might be where algae could grow. If you're close to your minimum, part of your pool might be at risk for algae by the end of the day.
    10,500 gal IG, Topaz Pebble, auto-level
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    Re: Me vs. The Pool Guy

    I grab my test water from the exact same spot each time.

    I dunk my bottle in up to my elbow. I don't think I'm growing any more (46 ) so that should be consistent.

    As long as you do it the same, you can just rely on your own test results and any changes should be accurate even if your actual numbers are off a bit.
    ----Chris----
    25k IG/Spa Figure 8, 18x36, Pebble Sheen Blue Granite, Sta-Rite S8M150 Cartridge Filter, Pentair 460805 400k BTU Heater & 011018 IntelliFlo VarSpd
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    Re: Me vs. The Pool Guy

    Quote Originally Posted by BuckeyeChris View Post
    if your water isn't circulating, that's probably the better reading to have, as it shows where the weak point in your water might be where algae could grow.
    This is an interesting observation - I may have to take a few samples around my pool & find my weak point. That would then be my control location.

    Quote Originally Posted by Agent99 View Post
    As long as you do it the same, you can just rely on your own test results and any changes should be accurate
    I wholeheartedly agree! If you're wrong, but consistently wrong, that's so much better than being inconsistent!
    16,661 gal IG PebbleTec w/ Spa; 60 ft2 Jandy DE filter, 2 HP Jandy Variable Speed pump; 2 skimmer; 400K BTU Jandy heater; Polaris Sport; opened 9/15/14; TF-100 test kit

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    Re: Me vs. The Pool Guy

    Yeah, if you are a person with lots of free time, you could find the batch of water in your pool that always seems to have the lowest FC and then make sure that's above the minimum. But really, just adjust your filter times and stay 1 PPM above the minimum and you'll be fine.
    10,500 gal IG, Topaz Pebble, auto-level
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    ColorLogic Mutlicolor LED lamp. Taylor 2006+speed stir

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    Re: Me vs. The Pool Guy

    When I was trying to figure out my pool this spring in my first year of ownership, I was having trouble with the DPD test- I was getting no FC reading, but if you waited a few minutes, the sample would turn pink, which I mistakenly thought was FC. I realized my mistake when I pulled a sample of water (from the same place I always do) and the sample turned deep pink with the addition of the DPD powder (it had been a little while since I added bleach). So, I somehow tapped into a pocket of FC that hadn't been mixed in, as I could not repeat the deep pink color in the 1-2 tests I did immediately after....
    20000 gallon vinyl liner in ground pool
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    Re: Me vs. The Pool Guy

    One thing that you need to correct is the depth of the water sample you use, 6"-8" is not deep enough, make sure you are getting it from 12"-18" deep.

    With DPD testing the test has an error accuracy of +-1ppm in the range you are testing. For more accuracy use the FAS/DPD test.
    16k gal plaster with raised spa, Jandy DEV60 filter, 2 HP 2-speed SHPF Jandy Stealth pump
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    Re: Me vs. The Pool Guy

    What's the thought process on taking a sample directly in front of a return that is about 8'inches deep?
    What's the thought process on taking a sample at a less than optimal depth, but if it exceeds minimum, so would the deeper water, yes?
    Central TX / 12K GAL / IG / SWG / DE filter / Pentair SVRS & 3 swim jet pumps / Spa bench and jets / Single body of water / No heater.

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    Re: Me vs. The Pool Guy

    Please remember, TFP is about simplicity, not overthinking the way you manage your pool. If your pump has been running for 30 minutes prior to your test, it should not make a gnat's behind worth of difference where you take your sample. Your water should be blended just fine. Please take a sample from around 12".

    If you find you are getting significantly different readings by chasing a "hot spot" or any other technique. The chances are quite good that you need a new pump!!
    Dave S.
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    Re: Me vs. The Pool Guy

    What a coincidence with this thread....just last night, I decided to take my sample from the water coming out of my return after the pump had been running for about an hour.


    duraleigh,
    you had me with "If your pump has been running for 30 minutes prior to your test, it should not make a gnat's behind worth of difference where you take your sample. Your water should be blended just fine.", which is what I always thought, and then you finish it with "Please take a sample from around 12". I'm confused..
    23K gallon, IG, Vinyl, Hayward DE-3600 Filter, Raypak 406A Heater, Hayward 1.5HP SP2610X15 pump aka AO Smith UST1152, TF-100 Test Kit

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    Re: Me vs. The Pool Guy

    Quote Originally Posted by ping View Post
    ...make sure you are getting it from 12"-18" deep.
    I just measured from my hand to elbow: 14". I think I'm good.
    ----Chris----
    25k IG/Spa Figure 8, 18x36, Pebble Sheen Blue Granite, Sta-Rite S8M150 Cartridge Filter, Pentair 460805 400k BTU Heater & 011018 IntelliFlo VarSpd
    Liquidator, Fafco Solar Heat, Polaris PB460 Booster Pump w/280 cleaner, Katchaleaf Cover, TF100 Test Kit, FAKE MAIN DRAIN

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    Re: Me vs. The Pool Guy

    This is one reason I split up my pump run time. From 8p to 12a to circulate my newly added bleach, then from 8a -12p to have some circulation in the sun. The other reason is to spread out the skimming function so debris is on the surface for a shorter period of time.
    10,500 gal IG, Topaz Pebble, auto-level
    Hayward DE filter, 2HP Ecostar VSP, ProLogic PS-4, GVA actuators
    Cal Pools Wave Force Plus (wall return jets plus 2 floor pop-ups), Venturi Skimmer
    Water sheer, 2 wok pots, bubbler stem on the baja step
    ColorLogic Mutlicolor LED lamp. Taylor 2006+speed stir

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    Re: Me vs. The Pool Guy

    take a sample from around 12".
    Just a "good practice" technique.....I think mostly keeping you from pulling in any surface debris. Truth be told, it just might be irrelevant but it's one of those things that I do without thinking. Actually, my wife says that a good portion of my waking hours are spent that way.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Re: Me vs. The Pool Guy

    Versus me, who thinks without doing
    10,500 gal IG, Topaz Pebble, auto-level
    Hayward DE filter, 2HP Ecostar VSP, ProLogic PS-4, GVA actuators
    Cal Pools Wave Force Plus (wall return jets plus 2 floor pop-ups), Venturi Skimmer
    Water sheer, 2 wok pots, bubbler stem on the baja step
    ColorLogic Mutlicolor LED lamp. Taylor 2006+speed stir

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    Re: Me vs. The Pool Guy

    Some good pointers about simplicity and overthinking. Thanks.
    Central TX / 12K GAL / IG / SWG / DE filter / Pentair SVRS & 3 swim jet pumps / Spa bench and jets / Single body of water / No heater.

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    Re: Me vs. The Pool Guy

    Another thing to consider is that his test kit my bake in his truck all summer and may not be giving accurate readings.
    Indoor 20x40 35,000 gallon vinyl pool with 1.5 HP 2 speed Jandy FloPro pump, Hayward EC75 Perflex DE filter, 11 4x12 Techno-Solis solar panels w/ Aquasolar controller, Aquabot Turbo T Robot Cleaner. Also LMI metering chlorine dispenser pump and HotSpring Jetsetter
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    Re: Me vs. The Pool Guy

    I follow the recommendation from Taylor technologies and sample the water mid-pool, at more than "elbow depth".

    It's in the section titled "Work with a water sample that's representative of conditions in the pool as a whole." where they offer several good reasons.


    That being said, if I understand what I have been reading correctly, the TFPC recommendations are based on pool problems and measurements reported by TFP users. That must mean that the recommended levels are based on water samples from the deep end, if that's where most TFP users get their samples.

    The same would apply to any other popular interpretations, such as how to measure the volume of a sample. I'm using a 10 ml syringe I bought at the pharmacy, so I'm pretty sure I get the right volume but it seems to be too low according to the scale on the TF-100 vial. Assuming most TFP users don't use syringes to measure their water samples, the recommendations would then be based on slightly larger sample volumes ?


    Either way, the pool is crystal clear and that's the most important parameter. A nice bonus is that the pool store can go entertain themselves.
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    Re: Me vs. The Pool Guy

    Quote Originally Posted by Sparkle View Post
    I follow the recommendation from Taylor technologies and sample the water mid-pool, at more than "elbow depth".
    That would imply that you essentially need to get into the pool to do any testing, unless you have some rig that grabs water several feet out, several feet deep.


    Quote Originally Posted by Sparkle View Post
    The same would apply to any other popular interpretations, such as how to measure the volume of a sample. I'm using a 10 ml syringe I bought at the pharmacy, so I'm pretty sure I get the right volume but it seems to be too low according to the scale on the TF-100 vial. Assuming most TFP users don't use syringes to measure their water samples, the recommendations would then be based on slightly larger sample volumes ?
    Not sure I understand that question. All the tests are based on a known water sample size, such as 45 ml, 25 ml, or 10ml. As long as you're using the recommended sample size for the test, or following one of the known dilution/multiplication of results procedures, you should be fine.

    I use my various vials and the Taylor comparator and fill to the appropriate amount required for the test I'm doing at that time.
    Central TX / 12K GAL / IG / SWG / DE filter / Pentair SVRS & 3 swim jet pumps / Spa bench and jets / Single body of water / No heater.

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