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Thread: Help with CYA, TA and FC levels on SW Pool

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    Join Date
    Oct 2014
    Location
    Chico/California
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    Help with CYA, TA and FC levels on SW Pool

    First I would like to thank everybody for all the great information provided on this site. I have learned so much in the past week reading about FC, CYA, and other chemical levels, but I would appreciate some advice on my particular issues.

    I keep my pool covered when not in use. I have the pool filter running at a relative high speed for two hours per day when the booster pump is running the sweeper. Then when the booster pump turns off I reduce the speed of the main pump to circulate water and generate FC through the SWG for another three hours. I have to admit that I don't test my water very often, maybe every two weeks or so.

    A couple weeks ago I pulled the cover off and the pool was green with algae. I noticed that at the lower speed, the flow was insufficient and the SWG flow sensor was keeping the SWG cell from turning on. So I backwashed the DE filter, and cleaned the scale off the SWG. I went to the pool store and bought six pounds of BioGuard Shock (Sodium Dichlor). I turned the pump on high, turned on the booster pump/cleaner, and turned the SWG on the boost setting and adjusted the pH. Then I added the six pounds of shock, added two chlorine pucks to the skimmer basket, brushed the pool, and let everything run for about 10 hours. First thing the next morning I turned on the pump, cleaner and SWG and swept the pool again. The pool had cleared considerably and had turned from green to cloudy grey. I tested the water with my cheap tester and the chlorine reading was too dark to read.

    That night I found this awesome website and learned so much about all the things I have been doing wrong. Number one was trying to use my SWG in boost mode to clear up an active algae bloom. I always wondered why my FC reading was always coming out zero no matter how long I ran it. The pool store always recommended double shocking and then a maintenance shock once a week.

    So here is where I am at now:

    First I ordered the TF-100 kit which I should get next week. Then I had a water sample analyzed by the pool store on Tuesday (three days after applying the shock). I know based on what I have read not to trust the results, but they are all I have until next week:

    FC: 10.3
    CC: 0 (Deduced because they reported no difference between free chlorine and total chlorine)
    pH: 7.8
    TA: 122
    Adjusted Total Alk: 82
    CH: 535 (reported as Total Hardness not sure if that is only calcium hardness)
    CYA: 132
    Salt: 3450
    Temp (I measured it): 82

    The main issue I have been having for the past two years is that the SWG doesn't seem to generate FC like is used to when I first had it installed.

    After reading through the information on this site I am starting to think my high CYA level may be causing this. I also now realize that using the chlorine pucks in the winter instead of liquid chlorine, along with shocking weekly, along with very little rainfall the past two years may have caused these elevated CYA levels. Also, my TA level appears to be elevated too.

    I know I need to verify these numbers once I get my test kit next week, but it looks like I will need to do a water exchange to lower the CYA and then make sure TA is correct. Do you concur with this assessment? Are there any other recommendations you can suggest?

    Thanks in advance,
    Curtis

    P.S. Once I get the TF-100 I plan on measuring my pool levels much more frequently!
    28,000 gallons ~ In Ground Plaster ~ Pentair FNS Plus 48 DE Filter ~ Pentair Intelliflo Variable Speed Pump
    3/4 HP Booster Pump ~ Pentair IntelliChlor IC40 Salt Chlorine Generator Cell ~ Pool Built 1988 ~ TFTestkit TF-100

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    Mod Squad tim5055's Avatar
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    May 2014
    Location
    Columbia, SC
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    8,494

    Re: Help with CYA, TA and FC levels on SW Pool

    You got it, not much credence is given to pool store testing. While you would think that a "professional" would be the best, unfortunately in most cases it is quite the opposite. Between employees who blindly trust the word of chemical sales representatives and high school kids working in the pool store for the summer you end up with poor results from their testing.

    100 is the limit of the CYA test in the TF100 (but more acurate than the pool store test), so you have to do a diluted test. While the full instructions are in the Pool School, here is the short version. Mix 50% pool water with 50% tap water. Use this mixed sample as your test water. If still at a 100 you will need to dilute more. Here is a great chart by JamesW to explain dilution rates and what you multiply the results by to get an approximation of your CYA level.

    Pool water......Tap or distilled water.........Multiply result by

    ....1...................1................................2
    ....1...................2................................3
    ....1...................4................................5

    Once you verify your numbers tehn you can think about dumping water and SLAMing your pool .

    I can see you have been reading, but how much Pool School have you read? Start with these:
    ABCs of Water Chemistry
    Recommended Pool Chemicals
    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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    Join Date
    Oct 2014
    Location
    Chico/California
    Posts
    2

    Re: Help with CYA, TA and FC levels on SW Pool

    Thanks for the tips on diluting to determine the proper CYA level once I get the TF100 kit delivered. It is too bad the reports from pool stores can't always be trusted. My local store has had the same employees for the past couple years so at least the test are done in a consistent manner. They kept telling me that my chlorine was bound up and I needed to add the shock to "free it up". If I understand what I am reading here, I just never fully got rid of the original algae problem. The store employee would tell me I needed some product, but they could never explain to me in a way that made sense why my SWG wasn't putting out FC. It is frustrating, but I really appreciate the great information available here!

    -Curtis
    28,000 gallons ~ In Ground Plaster ~ Pentair FNS Plus 48 DE Filter ~ Pentair Intelliflo Variable Speed Pump
    3/4 HP Booster Pump ~ Pentair IntelliChlor IC40 Salt Chlorine Generator Cell ~ Pool Built 1988 ~ TFTestkit TF-100

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