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Thread: CYA drop tests are somewhat subjective...

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    CYA drop tests are somewhat subjective...

    Hi, another new pool owner. I ordered the TF100 test kit and tried it out today on CYA. I agree with other posters that it is very difficult to tell when the dot disappears. I put in the recommended amount of CYA to bring my freshly filled pool up to a CYA level of 40. In doing the test the dot mostly disappears at around 40, but really if you look very carefully you can see it ever so slightly even when the tube is completely full. I'm not sure how this subjective decision as to when the dot disappears is any more accurate than the subjective decision as to what color the test strips are. It appears that different lighting levels greatly affect the results, as does asking different people to read it. My wife sees it disappear completely at around 40, yet if she hands it to me I can see the dot.

    I wonder if someone could make a little blacked out tube with an LED in the bottom, and a light sensor in the cap that would give precise light transmission readings based on how occluded the solution is. This could be calibrated before testing to adjust for differences in LED light output due to battery drain or aging of the electronics by using a calibration solution that has a known occlusion level (either premixed or mixed by the consumer as needed). I know this would take some work, but these days programmable microchips would make it pretty cheap to produce. Anyone here have more free time than me?

    Am I putting too much weight on this test? Is it really not that important? Should I shoot for a higher CYA level just to be on the safe side?

    In case someone wants to double check my math on the CYA I added, I added 2lb of dry 96% pure CYA to 6300 gallons of fresh well water.

    Thanks for any advice.
    Second year pool operator. Summer Escapes 18' round x 42" above ground printed vinyl with Sta-Rite 200 lb sand filter and 1 hp pump. BBB Method.

  2. Back To Top    #2
    linen's Avatar
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    Re: The dot mostly disappears at around 40

    Welcome to tfp, psteichen

    Yes the cya test can be challenging. Make sure it is sunny and you stand with the sun to your back with the tube at waist level. In the extended test kit instructions there is a link to Taylor's site that has a picture of what you are looking for.

    The test is important since it tells you how much FC you should be maintaining.

    Quote Originally Posted by psteichen
    In case someone wants to double check my math on the CYA I added, I added 2lb of dry 96% pure CYA to 6300 gallons of fresh well water.
    That should have got you to about 40 ppm cya if you are sure you started at 0 (didn't add any or use trichlor or dichlor).

    How did you add it?

    It can take up to a week for granular cya to show up in test.
    TFP Expert who uses Pool School and my TF100 test kit along with PoolMath for my: Round 11K gallon AGP with deep end, 20" sand filter, Matrix 1hp 2spd, 6 2ftX20ft solar panels (and solar cover!), Intex SWCG (copper bars disconnected) and a Rubadub hot tub (chlorine). The SLAM process is not finished until: 1. CC < 0.5 ppm, 2. An OCLT < 1.0 ppm and, 3. The water is crystal clear.

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    Butterfly's Avatar
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    Re: The dot mostly disappears at around 40

    Yep, you got about 40 CYA in there

    Did you
    Stand outdoors with your back to the sun and hold the view tube at about waist level. If sunlight is not available, find the brightest artificial light you can.
    Here's a link to Extended Test Kit Instructions.
    It includes a link to Taylor w/visuals on the test procedure: extended-test-kit-directions-t25081.html

    Here's a link to the TFTestKit.net CYA video: http://www.youtube.com/watch?v=NxaqoW-_MCs
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    Re: The dot mostly disappears at around 40

    Dave (TFT) also sells a 50ppm CYA Standard solution for $8.95. You can use that to calibrate your technique, as it were. I think it's a great way for a beginner to gain confidence in their technique. I wish I had known about it when I first started doing my own CYA tests many moons ago.

    http://tftestkits.net/R-7065-CYA-Sta...ution-p34.html

    He also has them for TA and CH.
    Current: 28,000G 18'x36' I/G AnthonySylvan Plaster; Waterway 60 sq.ft. DE Filter; 1.0hp x 1.65 SF Two-Speed (B2982) WhisperFlo; 2004-Present
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    Ancient Taylor K-2000, upgraded with Taylor CH, TA, and FAS-DPD, and TFT CYA tests.

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    Isaac-1's Avatar
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    Re: The dot mostly disappears at around 40

    I find a lot of times what I am seeing is the reflection of the top of the tube thinking it is the black dot when the dot has in fact vanished. As to the strip test, the big problem with most of them is the scale for the color range when your choices are 0, 75, 125 and 175 or some such, 3 of the 4 readings are above the suggested range, which makes it very hard to tell where you are inbetween the first 2 shades.
    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: The dot mostly disappears at around 40

    Quote Originally Posted by linen
    ...Make sure it is sunny and you stand with the sun to your back with the tube at waist level.

    ...That should have got you to about 40 ppm cya if you are sure you started at 0 (didn't add any or use trichlor or dichlor).

    ...How did you add it?

    It can take up to a week for granular cya to show up in test.
    Well, there hasn't been full sun here since I put up the pool, but I did try to use bright house lighting. Your point about needing to wait 1 week before testing may be an issue. I added the granular CYA 4 days ago by dissolving it in water and then poured in slowly in front of the return jet. I'll try the test again in a few more days.

    But the fact that this test is somewhat subjective is still disappointing. I wish I had known to order the 50ppm test fluid with my kit. Now I'd have to pay shipping again.

    Thanks for the ideas everyone!
    Second year pool operator. Summer Escapes 18' round x 42" above ground printed vinyl with Sta-Rite 200 lb sand filter and 1 hp pump. BBB Method.

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    Mod Squad jblizzle's Avatar
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    Re: CYA drop tests are very subjective...

    All the other tests give the sense of a required accuracy ... in reality, there is no need to be that exact. The CYA test at best is +/- 15ppm ... just pour the sample back and forth a few times and see if you consistently get a similar result ... then don't sweat it and trust that.

    Try doing the test with the same sample in varying light conditions and you will see if/how it impacts the result.
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