Become a TFP Supporter Pool Math Forum Rules Pool School
Results 1 to 7 of 7

Thread: Big FC drop during the day... but passing OCLT

  1. Back To Top    #1

    Join Date
    May 2012
    Location
    Houston, TX
    Posts
    37

    Big FC drop during the day... but passing OCLT

    Recent convert to the BBB method. Testing with TF-100, and my numbers are in line with the recommended values for CC, CYA, pH, TA. 18000 gallon, in ground, gunnite pool. Was using trichlor until I noticed brown stains and found my CYA= 100+.

    Current values:
    FC= 1
    CC= 0-0.5
    pH= 7.2 (lowered with MA since I am going to work on the stains which could be iron vs Ca scaling)
    TA= 110
    CYA= 35

    So here is my issue- shocked with 6%chlorine up to 13 based on the Cl/CYA chart. Next morning FC fell to 12. At the end of that day the FC had fallen to 7 - sunny day here in Houston, 3 people swam for 1 hr. The following morning the FC was 6. No swimming that day (Memorial Day), now at night the FC is 0.5-1. Added 6% bleach with a target of 10 (to give me some leeway for tomorrow).

    I don't think I have any organics/algae since I passed the OCLT. Water is very clear. I thought the daily drop in FC was supposed to be 2-3 not 5-6. Just want to make sure that I'm not missing something.

    Thanks!
    ___________________________________________________

  2. Back To Top    #2
    linen's Avatar
    Join Date
    Jul 2010
    Location
    Twin Cities, MN
    Posts
    8,649

    Re: Big FC drop during the day... but passing OCLT

    Let me see if I have this correctly, you experienced a drop of 6 to 1 ppm during one day? No signs of CC?

    That is a little high, though each pool situation is different. How much sun does your pool get? How hot has it been?

    You may want to repeat the OCLT just to be sure.

    If the OCLT passes again, you might want to raise the CYA level to 50 ppm to protect your chlorine from the sun a little better.
    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.

  3. Back To Top    #3

    Join Date
    May 2012
    Location
    Houston, TX
    Posts
    37

    Re: Big FC drop during the day... but passing OCLT

    The pool gets 10hours of full sun daily, if not more. Temps have been in the low 90's here. Passed the OCLT Sat and Sun nights. Noticed the FC drops on Sun and Mon. Sat night the CC was zero, Sun night the solution turned just a mere blush of pink, but I added a drop of reagent to clear it up, so I counted it as CC=0.5. I will try and bump the CYA up, and hope that helps to stabilize the chlorine.

    To be on the safe side, should I add some polyquat60 algaecide? I need the FC to be near zero to address the stains but I'm nervous about the large daily drops in FC, since I won't be able to work on the stains for a week or two.
    ___________________________________________________

  4. Back To Top    #4

    In the Industry

    duraleigh's Avatar
    Join Date
    Apr 2007
    Location
    Sebring, Florida
    Posts
    30,085

    Re: Big FC drop during the day... but passing OCLT

    I always go back to our old mantra....

    There's ONLY two things that consume chlorine, sunlight and organics. If you pass the OCLT and perform it correctly, you have no organics in the pool.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

  5. Back To Top    #5

    Re: Big FC drop during the day... but passing OCLT

    Quote Originally Posted by caliking
    Recent convert to the BBB method. Testing with TF-100, and my numbers are in line with the recommended values for CC, CYA, pH, TA. 18000 gallon, in ground, gunnite pool. Was using trichlor until I noticed brown stains and found my CYA= 100+.

    Current values:
    FC= 1
    CC= 0-0.5
    pH= 7.2 (lowered with MA since I am going to work on the stains which could be iron vs Ca scaling)
    TA= 110
    CYA= 35

    So here is my issue- shocked with 6%chlorine up to 13 based on the Cl/CYA chart. Next morning FC fell to 12. At the end of that day the FC had fallen to 7 - sunny day here in Houston, 3 people swam for 1 hr. The following morning the FC was 6. No swimming that day (Memorial Day), now at night the FC is 0.5-1. Added 6% bleach with a target of 10 (to give me some leeway for tomorrow).

    I don't think I have any organics/algae since I passed the OCLT. Water is very clear. I thought the daily drop in FC was supposed to be 2-3 not 5-6. Just want to make sure that I'm not missing something.

    Thanks!
    about 3 weeks ago I was losing 3-4 ppm per day from my pool in austin with a CYA around 30. I bumped it to 45-50 and now lose about 1-2ppm. I think you need more CYA. You will need to keep your FC at around 5.
    17,800 gallon, IG pool, 595 sq feet (17x35x4.5 avg rectangle), Hayward 525 cartridge filter, diamondbrite, 2 hp 2 speed hayward tristar filter, Stenner 45mhp10 automatically chlorinating

  6. Back To Top    #6
    Mod Squad Bama Rambler's Avatar
    Join Date
    Jun 2009
    Location
    SouthWest Alabama
    Posts
    22,349

    Re: Big FC drop during the day... but passing OCLT

    Just chiming in here. Im our pool it makes a big difference in how much FC we lose per day if our CYA is 50 to 60 as opposed to 30 to 40.
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/¼hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
    Pool School ----- Pool Math ----- TF-Test Kit

  7. Back To Top    #7

    Join Date
    May 2012
    Location
    Houston, TX
    Posts
    37

    Re: Big FC drop during the day... but passing OCLT

    Thanks for the info everyone. I won't tell my wife that the CYA is too low now because she wasn't happy when I drained the pool for the second time recently to lower the CYA!
    ___________________________________________________

Posting Permissions

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