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Thread: FC & pH Readings Change After Initial Readings

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    FC & pH Readings Change After Initial Readings

    Background info:

    No current issues with pool; water looks good, etc.

    15k Gunite Pool DE Filter

    Current filter PSI: 15

    Location: Dallas, TX

    Test Kit: Taylor Kit distributed by Leslie's. Purchased at Leslie's Pool Supply. I don't know the Taylor kit # but it's the standard kit with the rectangular dual test tubes with a FC range of 0-5.

    I recently changed to Bleach (June 7 '14) and discontinued Trichlor 3" tablets in Chlorinator.

    I rarely use Cal Hypo to shock. Pool seems to be going well with a FC level maintained between 7-12 (recommended range according to the Pool School online calculator with my current CYA level)


    Current readings (test every other day in summer season)

    FC: 5+ initial reading

    pH: 7.2 initial reading. Added Muriatic Acid 2 days ago to lower TA. Expect pH to increase next test. It's been climbing recently. Pool is aerated some due to the Jet Return positions.

    CC: 0

    TA: 100-110

    CYA: 90 the last time I checked on June 18 (2014). I'm waiting for a while to see if evaporation, discontinued Trichlor use, and water top-offs will lower CYA before draining some water.

    CH: 350 but haven't checked it since April (2014). My city water here has, I believe, a higher than normal CH content out of the faucet (~90).

    Average water temp in afternoon: 84-88F

    Latest CSI: -.21


    Quote Originally Posted by JasonLion View Post
    It means your PH is 7.6. The reading is correct for the first 30 seconds to a few minutes (the exact time varies) and after that it will often drift.
    Jason,

    Does this also happen when measuring FC? For example, I tested my pool today and the initial reading was 5+ (over the range of my Taylor kit). A few minutes later, the reading appeared to be about 2.0

    Same thing with the pH: Initial reading: 7.2 Delayed reading: 7.5
    - Pool Type: 15k Gal Gunite IG non-SWG / Built 1988
    - Pump: Pentair Challenger / Sweep Pump: Letro Model LA01N .75HP Single-speed / 6 hrs-day (1 turnover)
    - D.E. Filter: OEM: Nautilus (Pentair) #NS 36 / 36 Sq Ft / D.E. Charge: 3.6 Lb
    - Pentair 4-wheel Sweep LL505G - Booster Pump runs ~2 hrs/day

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    Mod Squad tim5055's Avatar
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    Re: FC & pH Readings Change After Initial Readings

    Quote Originally Posted by Scoop View Post
    Does this also happen when measuring FC? For example, I tested my pool today and the initial reading was 5+ (over the range of my Taylor kit). A few minutes later, the reading appeared to be about 2.0

    Same thing with the pH: Initial reading: 7.2 Delayed reading: 7.5
    I'm not Jason, but yes - all tests are meant to be read in a reasonable amount of time, i.e. not left sitting for minutes.

    You probably have the Taylor K-2005. You can pick up the FAS-DPD reagents from TFTestkits.net to make it the same as a K-2006
    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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    JasonLion's Avatar
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    Re: FC & pH Readings Change After Initial Readings

    Evaporation does not lower the CYA level. Water evaporates, but CYA does not. As water evaporates the CYA level goes up just slightly. Then when you top off the pool the CYA level goes back down to where it started originally. CYA does go down very slowly over time, but not because of evaporation.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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    Re: FC & pH Readings Change After Initial Readings

    Quote Originally Posted by tim5055 View Post
    I'm not Jason, but yes - all tests are meant to be read in a reasonable amount of time, i.e. not left sitting for minutes.

    You probably have the Taylor K-2005. You can pick up the FAS-DPD reagents from TFTestkits.net to make it the same as a K-2006
    Thanks for the info. I looked at the K-2006 kit a few years ago but passed on it at that time. I read about the FAS testing a few years ago but haven't reviewed the info for a few years.

    Is this correct? ↓

    - The "FAS" testing refers to that powder which allows for FC readings up to 20 ppm (or is it 50?).

    - The test also allows for a larger CC test range than conventional tests with the 0-5 test tubes.


    I was searching for the R-0870-I powder and saw another Taylor kit that I hadn't seen before: K-1515-C

    It appears to be an add-on kit for extended-range FC/CC testing. I might get that one.




    Quote Originally Posted by JasonLion View Post
    Evaporation does not lower the CYA level. Water evaporates, but CYA does not. As water evaporates the CYA level goes up just slightly. Then when you top off the pool the CYA level goes back down to where it started originally. CYA does go down very slowly over time, but not because of evaporation.
    Thanks for the info. I remember that now, memory-jog. I was hoping to avoid a partial drain.
    - Pool Type: 15k Gal Gunite IG non-SWG / Built 1988
    - Pump: Pentair Challenger / Sweep Pump: Letro Model LA01N .75HP Single-speed / 6 hrs-day (1 turnover)
    - D.E. Filter: OEM: Nautilus (Pentair) #NS 36 / 36 Sq Ft / D.E. Charge: 3.6 Lb
    - Pentair 4-wheel Sweep LL505G - Booster Pump runs ~2 hrs/day

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    Mod Squad jblizzle's Avatar
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    Re: FC & pH Readings Change After Initial Readings

    The K-1515 is the Taylor FAS-DPD chlorine test ... you can get something equivalent same Taylor regents but with a higher quantity from Dave at tftestkits.net: FAS-DPD Chlorine Test

    It will test up to 50ppm and will test FC and then CC in increments of 0.5ppm (or 0.2ppm if you use a 25 ml sample, but that is not needed).
    Jason, TFP Moderator
    18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
    500 sqft Heliocol solar panels, ThePoolCleaner, TF-100 test kit w/ SpeedStir
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    Re: FC & pH Readings Change After Initial Readings

    Quote Originally Posted by jblizzle View Post
    The K-1515 is the Taylor FAS-DPD chlorine test ... you can get something equivalent same Taylor regents but with a higher quantity from Dave at tftestkits.net: FAS-DPD Chlorine Test

    It will test up to 50ppm and will test FC and then CC in increments of 0.5ppm (or 0.2ppm if you use a 25 ml sample, but that is not needed).
    Thanks for the info. That FC/CC kit looks like the one I'll get from the site link you provided.
    - Pool Type: 15k Gal Gunite IG non-SWG / Built 1988
    - Pump: Pentair Challenger / Sweep Pump: Letro Model LA01N .75HP Single-speed / 6 hrs-day (1 turnover)
    - D.E. Filter: OEM: Nautilus (Pentair) #NS 36 / 36 Sq Ft / D.E. Charge: 3.6 Lb
    - Pentair 4-wheel Sweep LL505G - Booster Pump runs ~2 hrs/day

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    Mod Squad jblizzle's Avatar
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    Re: FC & pH Readings Change After Initial Readings

    Might I also recommend one of their fabulous liquid filled pressure gauges while you are ordering to save on shipping? Cheaper than the junk you will find locally.
    And the SpeedStir is also a great add-on
    Jason, TFP Moderator
    18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
    500 sqft Heliocol solar panels, ThePoolCleaner, TF-100 test kit w/ SpeedStir
    Pool School + Test Kit + PoolMath = A TROUBLE FREE POOL
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    Re: FC & pH Readings Change After Initial Readings

    Quote Originally Posted by jblizzle View Post
    Might I also recommend one of their fabulous liquid filled pressure gauges while you are ordering to save on shipping? Cheaper than the junk you will find locally.
    And the SpeedStir is also a great add-on
    Thanks again for the info

    I think I see the glycerin-filled PSI Gauge .

    I like the design. Is the glycerin mainly to protect the gauge from freezing climates?

    I'd probably have to add a pipe extension for gauge clearance on my SS DE tank to mount that gauge since it appears to be bigger/taller (2.5") than the standard-sized gauges.

    That's easy though, Home Depot, etc. I like the scaling 0-30 PSI, easier to track DE PSI readings.

    Whoever the site Admin is, they're giving excellent advice here:

    "It is a good habit to check your filter PSI every time you walk past the pump and especially when you turn the pump on. Even a variation of 1/2 pound is easily detectable with these nice gauges."

    I've been backwashing using the PSI reading, for a few years now, instead of going by the local pool store's once/month recommendation.

    SpeedStir I bought one of those a couple years ago after reading about them at this forum.
    - Pool Type: 15k Gal Gunite IG non-SWG / Built 1988
    - Pump: Pentair Challenger / Sweep Pump: Letro Model LA01N .75HP Single-speed / 6 hrs-day (1 turnover)
    - D.E. Filter: OEM: Nautilus (Pentair) #NS 36 / 36 Sq Ft / D.E. Charge: 3.6 Lb
    - Pentair 4-wheel Sweep LL505G - Booster Pump runs ~2 hrs/day

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    Mod Squad jblizzle's Avatar
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    Re: FC & pH Readings Change After Initial Readings

    Dave, the owner of this forum, also owns and runs tftestkits

    I am not sure the glycerin protects it in the winter or not. If you close your pool, you should also remove and store the gauge inside.

    Also, we recommend filter cleaning when the pressure rises 20-25% over the clean pressure.
    Jason, TFP Moderator
    18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
    500 sqft Heliocol solar panels, ThePoolCleaner, TF-100 test kit w/ SpeedStir
    Pool School + Test Kit + PoolMath = A TROUBLE FREE POOL
    If you found TFP helpful and we saved you money ... Become a TFP Supporter!

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    Re: FC & pH Readings Change After Initial Readings

    Thanks for the info.

    I have a question about the FAS/DPD Chlorine & CC's Test Kit from Dave's site.

    Is the Sample Tube in this kit the same diameter size as the Taylor PN 9198 Tube? In other words, does the Sample Tube from Dave's site fit on the SpeedStir base?
    - Pool Type: 15k Gal Gunite IG non-SWG / Built 1988
    - Pump: Pentair Challenger / Sweep Pump: Letro Model LA01N .75HP Single-speed / 6 hrs-day (1 turnover)
    - D.E. Filter: OEM: Nautilus (Pentair) #NS 36 / 36 Sq Ft / D.E. Charge: 3.6 Lb
    - Pentair 4-wheel Sweep LL505G - Booster Pump runs ~2 hrs/day

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    Mod Squad jblizzle's Avatar
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    Re: FC & pH Readings Change After Initial Readings

    They are slightly different vials, but they all work on the SpeedStir. The Taylor tubes are a bit thicker and a good bit more expensive.
    Jason, TFP Moderator
    18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
    500 sqft Heliocol solar panels, ThePoolCleaner, TF-100 test kit w/ SpeedStir
    Pool School + Test Kit + PoolMath = A TROUBLE FREE POOL
    If you found TFP helpful and we saved you money ... Become a TFP Supporter!

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    Re: FC & pH Readings Change After Initial Readings

    for all the info here.
    - Pool Type: 15k Gal Gunite IG non-SWG / Built 1988
    - Pump: Pentair Challenger / Sweep Pump: Letro Model LA01N .75HP Single-speed / 6 hrs-day (1 turnover)
    - D.E. Filter: OEM: Nautilus (Pentair) #NS 36 / 36 Sq Ft / D.E. Charge: 3.6 Lb
    - Pentair 4-wheel Sweep LL505G - Booster Pump runs ~2 hrs/day

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