Become a TFP Supporter Pool Math Forum Rules Pool School
Page 1 of 2 12 LastLast
Results 1 to 20 of 37

Thread: Clear water but dropping FC

  1. Back To Top    #1

    Join Date
    Feb 2015
    Location
    The Woodlands TX
    Posts
    45

    Clear water but dropping FC

    Hello everyone!

    My situation is pretty much the way the title sounds. Last week, after a winter of only occasional attention, I noticed my pool had some slight green along the walls and floor. I ran the numbers, and they came out looking like this...

    FC - 0
    CC - 0
    pH - 7.8
    TA - 70
    CYA - 30

    I poured 121 oz Clorox 8.25% in the pool, and brushed the sides and bottom. I also vacuumed. Each of the next 3 days I added one bottle of Clorox. The FC would come in around 10 to 12, CC at 0.5. Within a day or so, the pool became clear, and the green disappeared. All good so far.

    I ran the OCLT each of the last two evenings, and I am losing about 1.5 each time. Specifically, last night my reading was 10.0, CC 0.5. This morning I was at 8.5 and 0.5. This afternoon, I tested and got FC 6.0 and CC 0.5. The pool still looks clear with no green accumulation. I also backwashed the filter this morning.

    Should the high chlorine drop in the OCLT concern me? Everything looks good, and the numbers are close, but not perfect. What do you think?
    12,000, IG 1992, 4.5' center/3' each end, Pentair FNS-60 DE Filter (2015)
    PebbleSheen installed 2015
    Pentair Superflo VS installed May 2016
    TF-100 Test Kit
    Dolphin Nautilus Plus Robot

  2. Back To Top    #2
    Texas Splash's Avatar
    Join Date
    Jun 2014
    Location
    South-Central Texas, Marion/San Antonio
    Posts
    12,947

    Re: Clear water but dropping FC

    Red, don't let the clear water fool you. It looks to me as though you simply need to employ a "SLAM" and knock that algae out for good. Simply adding one gallon of bleach each day won't do it. You'll need to "maintain" the required SLAM FC level until you pass all 3 SLAM criteria. With a CYA of 30, your SLAM/Shock FC level should be maintained at "12" - 24 hrs per day until the SLAM is complete. If everything is done as noted on the SLAM page (link below in my sig) you should do just fine. Let us know if you have any more questions.

    Oh - don't forget to lower the pH to 7.2 - 7.5 before raising the FC to 12 for the SLAM.
    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
    Vital Links: POOL SCHOOL, RECOMMENDED LEVELS, RECOMMENDED CHEMICALS, Poolmath Calculator, SLAM, Chlorine/CYA CHART.
    If you enjoyed your TFP experience, please consider donating to Support TFP!

  3. Back To Top    #3

    Join Date
    Feb 2015
    Location
    The Woodlands TX
    Posts
    45

    Re: Clear water but dropping FC

    I was afraid that was where this was heading. I appreciate the advice, and will update on my progress.
    12,000, IG 1992, 4.5' center/3' each end, Pentair FNS-60 DE Filter (2015)
    PebbleSheen installed 2015
    Pentair Superflo VS installed May 2016
    TF-100 Test Kit
    Dolphin Nautilus Plus Robot

  4. Back To Top    #4
    Mod Squad pooldv's Avatar
    Join Date
    Aug 2012
    Location
    DFW, TX
    Posts
    23,994

    Re: Clear water but dropping FC

    I have had algae and clear water. Good luck with your SLAM!
    TFP Moderator
    If TFP helped you or saved you money - Become a TFP Supporter! <--Click here
    2012 build and pics, 20k gal gunite, black onyx pebblesheen, OK flagstone, IntellifoVS, cart filter w/Pleatco, IC40 SWG, Solartouch, 5 12'x4' solar panels, HP50HA heat pump, 8mil solar cover, borates, TF-100 test kit, SONOS, Doheny's Discovery Robot, hot tub on bleach

  5. Back To Top    #5
    Mod Squad YippeeSkippy's Avatar
    Join Date
    Jan 2012
    Location
    'burbs of Augusta, Georgia
    Posts
    6,479

    Re: Clear water but dropping FC

    My pool is also 12,000 gallons and if my FC were zero, one gallon of 8.25% liquid chlorine would only bring it up to about 7.5 of FC.

    18 ounces=1ppm FC in my pool.

    You never had your FC high enough to actually kill all the algae. Please review the SLAM directions.

    Let us know how it goes
    My Amazon Smile for November12K Fiberglass IG, Infinity 4000 automatic cover, SWCG, Hayward Sand Filter, Hayward 1.5 Pump, Doheny Discovery Robot, Savi Melody LED pool lights, outdoor speakers and other assorted doo-dads. Sundance Altamar Hot Tub.
    Our pool build--> Our Pool Solved Our Sloping Yard Skippy's Cheap Pool Cooler -->Skippy's New Fountain

  6. Back To Top    #6

    Join Date
    Aug 2014
    Location
    Northern IL
    Posts
    4,615

    Re: Clear water but dropping FC

    Don't be afraid of a "slam". This may be the last time you have to do it in eons.

  7. Back To Top    #7

    Join Date
    Feb 2015
    Location
    The Woodlands TX
    Posts
    45

    Re: Clear water but dropping FC

    I probably used the wrong term in saying "afraid". After 8 months of reading this forum, and doing my own chemistry and maintenance, there is literally nothing about this pool that scares me...thanks to everyone here.

    OK, so last night I added 60 ounces of muriatic acid to reduce the pH in preparation for the SLAM this morning. This morning, my numbers looked like this...

    FC - 14
    CC - 0.5
    pH - 7.2
    CYA - 22

    I was a little surprised that my CYA had dropped further, but we did get a lot of rain last week. Should I do anything about the CYA now during the SLAM? Should I do anything to raise it once my SLAM is complete? Everything else looks to be pretty good.

    - - - Updated - - -

    Quote Originally Posted by YippeeSkippy View Post
    My pool is also 12,000 gallons and if my FC were zero, one gallon of 8.25% liquid chlorine would only bring it up to about 7.5 of FC.

    18 ounces=1ppm FC in my pool.

    You never had your FC high enough to actually kill all the algae. Please review the SLAM directions.

    Let us know how it goes

    You are correct. The first gallon took it to 7-7.5. The next day, an additional gallon took it from 5.5 to 12. Last night, I added one gallon to the existing 6.0 level, and this morning I am at 14. So, the numbers seem pretty consistent with what you predicted.
    12,000, IG 1992, 4.5' center/3' each end, Pentair FNS-60 DE Filter (2015)
    PebbleSheen installed 2015
    Pentair Superflo VS installed May 2016
    TF-100 Test Kit
    Dolphin Nautilus Plus Robot

  8. Back To Top    #8
    Mod Squad JVTrain's Avatar
    Join Date
    Feb 2014
    Location
    Central Minnesota
    Posts
    5,079

    Re: Clear water but dropping FC

    I would get enough CYA in the pool to get it to 30, but only just enough. It could be a testing error as the CYA test is a bit subjective and can vary based on the lighting when the test is performed. Consider retesting before adding CYA. Once you complete the SLAM, I'd certainly get the CYA up to 40 or 50 based on your location. Rain won't drop your CYA by that much either. If the test was accurate, you lost 8 ppm CYA. In order to accomplish that, you'd have to replace 25% of your water.
    Joel - TFP Moderator - Minnesota - **Become a TFP Supporter!** Helpful Links: ABCs of Pool Water Chemistry - SLAM Procedure - Chlorine/CYA Chart
    40x20 Pool: 32K Gallons * Vinyl * Bleach Chlorination * Hayward S270T Sand Filter * Pentair SuperFlo 1 HP * Teledyne/Laars Heater * AquaVac Tigershark * TF-100 w/ SpeedStir
    Isolated Spa - 345 Gallons

  9. Back To Top    #9
    Mod Squad pooldv's Avatar
    Join Date
    Aug 2012
    Location
    DFW, TX
    Posts
    23,994

    Re: Clear water but dropping FC

    Quote Originally Posted by RedScare View Post
    I probably used the wrong term in saying "afraid". After 8 months of reading this forum, and doing my own chemistry and maintenance, there is literally nothing about this pool that scares me...thanks to everyone here.
    Good answer!

    I would leave CYA where it is for now.
    TFP Moderator
    If TFP helped you or saved you money - Become a TFP Supporter! <--Click here
    2012 build and pics, 20k gal gunite, black onyx pebblesheen, OK flagstone, IntellifoVS, cart filter w/Pleatco, IC40 SWG, Solartouch, 5 12'x4' solar panels, HP50HA heat pump, 8mil solar cover, borates, TF-100 test kit, SONOS, Doheny's Discovery Robot, hot tub on bleach

  10. Back To Top    #10

    Join Date
    Feb 2015
    Location
    The Woodlands TX
    Posts
    45

    Re: Clear water but dropping FC

    I believe I have some trichlor tablets left over from my auto chlorinator days. Would you recommend running that for a few days after the SLAM is complete to boost CYA? Or, is their some other method that works better?
    12,000, IG 1992, 4.5' center/3' each end, Pentair FNS-60 DE Filter (2015)
    PebbleSheen installed 2015
    Pentair Superflo VS installed May 2016
    TF-100 Test Kit
    Dolphin Nautilus Plus Robot

  11. Back To Top    #11
    Mod Squad JVTrain's Avatar
    Join Date
    Feb 2014
    Location
    Central Minnesota
    Posts
    5,079

    Re: Clear water but dropping FC

    When increasing CYA, it's best to use just pure CYA. Check out Pool School - Recommended Pool Chemicals and the details on CYA and how to add it to your pool.

    Save the pucks for when you go out of town for a few days and have wiggle room with your CYA. Pure CYA can be bought at many big box stores that have a pool section. HTH is my favorite brand so far as it has finer granules that dissolve faster.
    Joel - TFP Moderator - Minnesota - **Become a TFP Supporter!** Helpful Links: ABCs of Pool Water Chemistry - SLAM Procedure - Chlorine/CYA Chart
    40x20 Pool: 32K Gallons * Vinyl * Bleach Chlorination * Hayward S270T Sand Filter * Pentair SuperFlo 1 HP * Teledyne/Laars Heater * AquaVac Tigershark * TF-100 w/ SpeedStir
    Isolated Spa - 345 Gallons

  12. Back To Top    #12
    Mod Squad pooldv's Avatar
    Join Date
    Aug 2012
    Location
    DFW, TX
    Posts
    23,994

    Re: Clear water but dropping FC

    Using up old trichlor is fine for adding CYA. The pucks are acidic so keep an eye on your PH. Once you run out of pucks just add CYA/stabilizer. I get mine in 4lb bottles from Lowes.

    Here is a handy page on pool chemicals, what they are, what they do and how to add them.
    Pool School - Recommended Pool Chemicals
    TFP Moderator
    If TFP helped you or saved you money - Become a TFP Supporter! <--Click here
    2012 build and pics, 20k gal gunite, black onyx pebblesheen, OK flagstone, IntellifoVS, cart filter w/Pleatco, IC40 SWG, Solartouch, 5 12'x4' solar panels, HP50HA heat pump, 8mil solar cover, borates, TF-100 test kit, SONOS, Doheny's Discovery Robot, hot tub on bleach

  13. Back To Top    #13

    Join Date
    Feb 2015
    Location
    The Woodlands TX
    Posts
    45

    Re: Clear water but dropping FC

    Great. Thanks!
    12,000, IG 1992, 4.5' center/3' each end, Pentair FNS-60 DE Filter (2015)
    PebbleSheen installed 2015
    Pentair Superflo VS installed May 2016
    TF-100 Test Kit
    Dolphin Nautilus Plus Robot

  14. Back To Top    #14
    Mod Squad pooldv's Avatar
    Join Date
    Aug 2012
    Location
    DFW, TX
    Posts
    23,994

    Re: Clear water but dropping FC

    Hey, don't listen to that other guy posting at the same time as I do! He says weird stuff!
    TFP Moderator
    If TFP helped you or saved you money - Become a TFP Supporter! <--Click here
    2012 build and pics, 20k gal gunite, black onyx pebblesheen, OK flagstone, IntellifoVS, cart filter w/Pleatco, IC40 SWG, Solartouch, 5 12'x4' solar panels, HP50HA heat pump, 8mil solar cover, borates, TF-100 test kit, SONOS, Doheny's Discovery Robot, hot tub on bleach

  15. Back To Top    #15
    Mod Squad JVTrain's Avatar
    Join Date
    Feb 2014
    Location
    Central Minnesota
    Posts
    5,079

    Re: Clear water but dropping FC

    Haha!

    My response was first both times so it must be right!

    Truth is... we're both right!
    Joel - TFP Moderator - Minnesota - **Become a TFP Supporter!** Helpful Links: ABCs of Pool Water Chemistry - SLAM Procedure - Chlorine/CYA Chart
    40x20 Pool: 32K Gallons * Vinyl * Bleach Chlorination * Hayward S270T Sand Filter * Pentair SuperFlo 1 HP * Teledyne/Laars Heater * AquaVac Tigershark * TF-100 w/ SpeedStir
    Isolated Spa - 345 Gallons

  16. Back To Top    #16

    Join Date
    Feb 2015
    Location
    The Woodlands TX
    Posts
    45

    Re: Clear water but dropping FC

    I suggest a cage match to determine who is correct.
    12,000, IG 1992, 4.5' center/3' each end, Pentair FNS-60 DE Filter (2015)
    PebbleSheen installed 2015
    Pentair Superflo VS installed May 2016
    TF-100 Test Kit
    Dolphin Nautilus Plus Robot

  17. Back To Top    #17
    Mod Squad tim5055's Avatar
    Join Date
    May 2014
    Location
    Columbia, SC
    Posts
    8,495

    Re: Clear water but dropping FC

    You are getting great advice, but I have a question. What are you using to measure CYA of "22"?
    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

  18. Back To Top    #18

    Join Date
    Feb 2015
    Location
    The Woodlands TX
    Posts
    45

    Re: Clear water but dropping FC

    I'm using the tube in the TF100 kit. The level did not quite reach the 20 mark. I estimated it to be at a 22 if the tube had markings that precise.

    - - - Updated - - -

    I did not get a chance to test yesterday evening. My last test was at 3:30 pm, with an FC level of 12. This morning, FC came in at 11. I will do an OCLT this evening to see how it looks.
    12,000, IG 1992, 4.5' center/3' each end, Pentair FNS-60 DE Filter (2015)
    PebbleSheen installed 2015
    Pentair Superflo VS installed May 2016
    TF-100 Test Kit
    Dolphin Nautilus Plus Robot

  19. Back To Top    #19
    Mod Squad tim5055's Avatar
    Join Date
    May 2014
    Location
    Columbia, SC
    Posts
    8,495

    Re: Clear water but dropping FC

    Quote Originally Posted by RedScare View Post
    I'm using the tube in the TF100 kit. The level did not quite reach the 20 mark. I estimated it to be at a 22 if the tube had markings that precise.
    You can't make assumptions like that. The scale on the tube is not linear so you can't say that half way between 20 & 30 is 25. Always round up for FC/CYA calculations, so in your case SLAM for a CYA of 30.
    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

  20. Back To Top    #20

    Join Date
    Feb 2015
    Location
    The Woodlands TX
    Posts
    45

    Re: Clear water but dropping FC

    I see. Speaking of chemistry interpretations, when testing the chlorine level, I have noticed that after letting the water sit for several minutes the previously clear water returns to a shade of pink. Is this a normal reaction? The water had been clear at the time of testing. It is only after sitting for at least a couple of minutes that the solution turned pink again.

    BTW, this evening's test came in at 11. So, only a drop of 1 ppm all day, after a drop of 1 ppm overnight. This looks very encouraging. Water is still clear.
    12,000, IG 1992, 4.5' center/3' each end, Pentair FNS-60 DE Filter (2015)
    PebbleSheen installed 2015
    Pentair Superflo VS installed May 2016
    TF-100 Test Kit
    Dolphin Nautilus Plus Robot

Page 1 of 2 12 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •