Become a TFP Supporter Pool Math Forum Rules Pool School
Results 1 to 3 of 3

Thread: Accuracy of FAS-DPD at high CL levels/high CYA

  1. Back To Top    #1

    Join Date
    Jun 2015
    Location
    Jackson, NJ
    Posts
    123

    Accuracy of FAS-DPD at high CL levels/high CYA

    As prompted by a Mod, I've started a new thread regarding the above.

    Using this as my backdrop: http://www.troublefreepool.com/conte...-Chlorine-Test and making special note of the last line of the page -
    • The precision of the measurement is plus or minus one drop when up to 10 drops of titrant are used, or plus or minus 10% of the final reading, when more than 10 drops of titrant are used.


    I had postulated how it would be possible to pass a OCLT if your CYA was up around 70 (or higher). Shock level for that is 27.5 - so most I'm sure would use 28 or maybe even 30. At 56 -60 drops to ascertain your levels, how can one pass a OCLT with a 2 drop max deviance if there could be up to a 6 drop margin of error on the test?

    I had offered it might be 'easier' for those of us with high CYA to just SLAM for a week, and if the pool is clear and the CCs are .5 or lower perhaps letting the FC drift down to 10 before doing the OCLT would yield better testing results.

    So - here we go. What am I missing?
    Last edited by s1njin; 07-21-2016 at 07:34 AM. Reason: Clarified CYA level
    42' natural free-form pool, vinyl lined, 6' deep end, 21,400 gallons
    2 HP Hayward Superpump, Hayward Aquarite SWG, AquaComfort 125k btu heat pump, 350lb Hayward Pro Series sand filter
    2 skimmers, 2 floor drains, 10 returns (6 in the pool, 2 in the steps, 2 in the swim-out)
    TF-100 Test Kit

  2. Back To Top    #2

    In the Industry

    duraleigh's Avatar
    Join Date
    Apr 2007
    Location
    Sebring, Florida
    Posts
    30,083

    Re: Accuracy of FAS-DPD at high CL levels/high CYA

    The OCLT was never intended to be scientifically bullet proof.

    It is a darn good indicator that you have eradicated the organics in your pool.

    Dropping the FC down to a range (like 10 ppm) that gives you some common sense results is a good idea.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

  3. Back To Top    #3

    Join Date
    Jun 2015
    Location
    Jackson, NJ
    Posts
    123

    Re: Accuracy of FAS-DPD at high CL levels/high CYA

    Thanks Dave. Would it be helpful to note something like this in the SLAM procedure?
    42' natural free-form pool, vinyl lined, 6' deep end, 21,400 gallons
    2 HP Hayward Superpump, Hayward Aquarite SWG, AquaComfort 125k btu heat pump, 350lb Hayward Pro Series sand filter
    2 skimmers, 2 floor drains, 10 returns (6 in the pool, 2 in the steps, 2 in the swim-out)
    TF-100 Test Kit

Posting Permissions

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