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Thread: First TF-100 Results - Not Good!

  1. Back To Top    #1

    Join Date
    Jul 2015
    Williamsburg, VA

    First TF-100 Results - Not Good!

    Hi All! Last summer was my first taking care of a pool and it didn't go so well. I've since discovered this website, ordered and received a T-100 test kit, and I just took my first water samples. The results are really, really bad!

    FC - 1.5
    CC - 0.5
    pH - 8.0
    TA - 200
    CH - 500
    CYA - 120

    It's strange to me that they are so bad as the pool is crystal clear. There is some black algae growing on the bottom and sides of the pool, but otherwise it looks really good. PoolMath tells me that I need to replace somewhere between 50-65% of the water to get everything back in line. That would be a major expense - is there any other way to fix these issues? Thanks for the help!

    20,000 Gallon IG Vinyl Pool : Hayward S-200 Sand Filter: 3/4 HP AO Smith Pump - 2 Speed : TF-100 Test Kit

  2. Back To Top    #2

    Join Date
    Jun 2015

    Re: First TF-100 Results - Not Good!

    Using pool math bring your pH and alkalinity in line. You need to quickly raise your FC with liquid bleach. Shock levels at 120 CYA will be 40 parts ppm or better to kill that algae. Maintain levels afterwards will be 12+ ppm. You can start doing partial replacements of water 6" at a time to see if you can get cya down to a more manageable level.
    18' x 38' Pool, 3' to 8' Depth
    Vinyl Liner
    Variable Speed Pump
    Sand Filter

  3. Back To Top    #3
    Mod Squad pooldv's Avatar
    Join Date
    Aug 2012
    DFW, TX

    Re: First TF-100 Results - Not Good!

    Welcome to TFP! Good job getting a great test kit and getting started on TFPC, you will be glad you did.

    With CYA at 120 it will take a lot of chlorine to maintain your pool. It will be much easier if you drain 50% and get your CYA to a manageable level.

    With CYA of 120 your chlorine levels are
    Minimum 10, never drop below 10 or algae will grow and pool is nkt sanitary
    Target 14, should be at or slightly above this at all times
    Shock 48, need to maintain FC at 48 during SLAM to clear the algae you have

    One of the biggest problems is the PH test is not valid when FC is above 10. It is important to maintain PH between 7.2 and 7.8.

    Chlorine level is set based on CYA and the Chlorine CYA Chart

    Here is the process to SLAM - Shock Level And Maintain your pool.
    TFP Moderator
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  4. Back To Top    #4
    Richard320's Avatar
    Join Date
    Jan 2010
    San Dimas, CA (LA County)

    Re: First TF-100 Results - Not Good!

    In the long term, it will probably be cheaper to drain and replace half the water. The amount of bleach you'll need to eradicate the algae will be HUGE, and at higher FC levels, you lose more to sunlight, so it's self-defeating. And with 120 CYA, your minimum FC is 9. Do you really want to cut it that close all the time just so you can check pH when FC is below 10? You can't get an accurate pH reading above 10 FC.

    Looks like water & sewer combined is about $10/ 1000 gallons there. 10,000 gallons is a hundred bucks. That's thirty gallons of bleach. Just to get to shock level (47 for 120 CYA) initially is going to take 11 gallons! And who knows how much beyond that? Just the added cost of all the R-0871 reagent when you have to use 100 drops every couple hours is substantial.

    And if you tell them it's for filling a pool, they might waive the sewer part, which halves the expense.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
    A pool is like a pet - you have to feed it every day, even the days you don't want to play with it!

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