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Thread: Very Low FC, Very High CC

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    Very Low FC, Very High CC

    I became a first-time pool owner when we purchased a home with a pool a couple of months ago. I'm in northern NJ and I hired a pool company to open it 10 days ago(mid-April). It is a 35,000 gal in-ground gunite pool. They put some 3" Tri-chlor tablets into the automatic feeder and 10lbs of Sodium-diclor into the pool as shock and also added an algaecide. The pool has a pressure DE filter. The floor of the pool was covered with a fine silt. I vacuumed and brushed it up several times and the filter required backwashing every day for a week. I was testing for Free Chlorine and was not getting a level so I shocked the pool 2-3 times using Sodium Di-chlor following the package directions (~4lbs per shock). Still very low FC. I brought a sample to a pool store and they found that my Total Chlorine was 7 and Free Chlorine was 0.8. All the other measures were fine (pH, stabilizer, alkalinity, etc.). I have stopped adding chlorine because I think I'm only making the problem worse. The water is looking pretty clear at this point with only a little bit of the silt left. Can you guys provide any advice? Will the Combined Chlorine drop on its own over time or do I need to do a massive addition of Chlorine? Weather is still cool here so we don't plan on swimming for 2-3 weeks. Thanks.

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    JasonLion's Avatar
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    Re: Very Low FC, Very High CC

    Welcome to TFP!

    Your first issue is that all of that dichlor is raising the CYA level very quickly. CYA is going to get way too high soon, if it hasn't gotten too high already.

    The second issue is that we really need reliable test results to know what is going on. Without reliable test results it is impossible to know what to do.

    The very high CC levels are suggestive of ammonia in the water. The solution is to SLAM the pool, see the directions in Pool School. Loosely speaking, a massive addition of chlorine, but not dichlor and not all at once.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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    Re: Very Low FC, Very High CC

    Thank you for the very quick reply! This is a great forum. I've read the articles on SLAMing and figured that was the right thing to do. I will stop using the Dichlor and invest in a good test kit. When I SLAM the pool should I target the FC level purely based on the CYA level? Do I need to take the amount of CC levels into account when determining how much Chlorine (bleach) to add? thanks
    35,000 gal, in-ground gunite
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    JasonLion's Avatar
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    Re: Very Low FC, Very High CC

    Just target the correct FC level based on your CYA level.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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    Re: Very Low FC, Very High CC

    Thank you sir! I'm using the TFP CYA/FC chart, then the PoolMath tool to determine how much bleach to use. I'll let you know how it goes.
    35,000 gal, in-ground gunite
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    Patrick_B's Avatar
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    Re: Very Low FC, Very High CC

    Welcome to the forum!

    Please do let us know how it goes, and if we can help.
    TFP Moderator
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    Mod Squad pooldv's Avatar
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    Re: Very Low FC, Very High CC

    Welcome to TFP! Please update your signature as shown here.

    Here is some info on test kits, Test Kit Comparison

    Here is some basic water chemistry info
    TFPC for Beginners
    ABC's of Pool Water Chemistry

    Glad you are using the FC/CYA chart, what is your CYA level? Have you found PoolMath?

    Read up and ask more questions.
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    Re: Very Low FC, Very High CC

    Thanks for the help so far. I've started SLAMing today and could use some more help.

    I am using a Taylor FAS-DPD kit to test for FC and CC. Here's what I have done so far:
    Started process at noon today. Before adding bleach (8.25%) FC=0.4, CC=1.8, CYA=20, pH=7.5, TA=70. I used pool math to target a shock FC of 10. I added 5 gal of 8.25% bleach. The water was pretty clear when I started.
    1 hr later I tested and FC=3, CC=2.5. I added another 5 gal of bleach
    Tested again in 1 hr FC=6, CC=2. I added 4 more gal of bleach
    1hr later FC=4.5, CC= 4.5. I was out of bleach at that point and had some diclor on hand. Since CYA was relatively low I added 8 lbs of NaDichlor.
    2 hrs later FC=4, CC=5.5

    I bought 12 more gal of bleach, but I'm not sure where to go from here. It seems like the CC is getting worse. Should I just keep added bleach? At this rate I'll need a ton. Will the FC ever reach 12? Will the CC chlorine just keep going up? Thanks for your help.
    35,000 gal, in-ground gunite
    Pressure DE filter
    2 HP Hayward Pump
    Solar Heating System

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    Mod Squad tim5055's Avatar
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    Re: Very Low FC, Very High CC

    Welcome to TFP!!

    Yes, just keep adding chlorine to adjust back up to shock level each time you test.

    CC may go up at first but should start coming down soon.
    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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    Re: Very Low FC, Very High CC

    Thank you!! I'll give another dose now and keep plugging along. Keep you posted.
    35,000 gal, in-ground gunite
    Pressure DE filter
    2 HP Hayward Pump
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    Re: Very Low FC, Very High CC

    To give you an idea why Cc is going up...

    You have something organic in the water - algae, ammonia, whatever. When you add bleach (FC), it attacks whatever is in the water, and gets converted to CC. So, the rising CC indicates your Slam is killing off that stuff in the water - that's a good indication actually!

    CC naturally dissipates in sunlight, but not as fast as you're producing it right now. As you finish the slam, your bleach consumption and CC production will taper off, and CC will then start to decline. Just keep adding bleach and give it time...
    15k in-ground plaster, Hayward C900 cartridge, 3/4hp single speed pump, Barracuda G2 cleaner, TF-100

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    Mod Squad pooldv's Avatar
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    Re: Very Low FC, Very High CC

    You can speed the process along by testing and adding more bleach every couple of hours if you can.
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    Casey's Avatar
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    Re: Very Low FC, Very High CC

    You probably have ammonia in the water since you state the pool is clear.

    Keep SLAMing the daylights out of it.
    I'd bet you my bikini you'll never get TFP water from a pool store!

    24' Sharkline Venture De Filter

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    Mod Squad kimkats's Avatar
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    Re: Very Low FC, Very High CC

    You are doing all of the right things!

    -Find TFP
    -Get test kit
    -asking questions
    -adding bleach and more bleach

    Keep it up and you will be clear forever!

    It is going to take some time to balance your pool. Well time and bleach.

    Good job!

    Kim
    TFP Moderator 33x52 round AG 25,600 gals Sand Filter 1.5hp Pump - 2 Speed, SLAM, Pool School, Recommended Levels, Recommended Chemicals, Pool Math, Chlorine/CYA Chart, TF-100 Test Kit

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    Re: Very Low FC, Very High CC

    Quote Originally Posted by Dcommerford View Post
    1hr later FC=4.5, CC= 4.5. I was out of bleach at that point and had some diclor on hand. Since CYA was relatively low I added 8 lbs of NaDichlor.
    2 hrs later FC=4, CC=5.5

    I bought 12 more gal of bleach, but I'm not sure where to go from here. It seems like the CC is getting worse. Should I just keep added bleach? At this rate I'll need a ton. Will the FC ever reach 12? Will the CC chlorine just keep going up? Thanks for your help.
    Since the CYA went up with your use of diclor, your target FC needs to go up as well. Double check the chart
    12500 AGP 2HP Sand filter
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    Patrick_B's Avatar
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    Re: Very Low FC, Very High CC

    John is correct, you now have more Cya, so it will now require more FC to do the same job.

    Don't fret over the CC, part of the SLAM process is getting them down. Yes, you will get to SLAM level of FC but it takes adding more and more FC until you do, and are able to maintain that level for some period of time. You'll learn how long that time is, and be ready to dose again to keep it there and not let it fall below. You will get there.
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    Re: Very Low FC, Very High CC

    Thanks everyone. I'm making good progress. I've increased my FC shock target to 12 as the CYA is now 30. Here's an update since last time:

    I've added 4 more doses of 8.25% bleach (5 gallons each time) over the last 24hrs. The first 3 readings ~2 hours post-bleach were pretty consistent at FC=1-3, CC=1. The last reading I just did was FC=12.5 and CC=1. I have never had a FC reading over 6. Feels like I'm turning a corner!! The DE filter needed to be back-washed also. The pressure went up 10 psi after I started SLAMing. I'll check in the morning. Got plenty of bleach on hand...
    35,000 gal, in-ground gunite
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    Casey's Avatar
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    Re: Very Low FC, Very High CC

    You're getting there! Keep going!
    I'd bet you my bikini you'll never get TFP water from a pool store!

    24' Sharkline Venture De Filter

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    Re: Very Low FC, Very High CC

    Here's an update. I completed the SLAM process on 5/13 when the pool passed the overnight chlorine test. The pool is looking great and chemistry is spot on (now have a TF-100 kit). As a recap, my SLAM took 7 days and over 50 gals of bleach. Definitely got the job done and ready for summer. Thanks everyone for the advice.
    35,000 gal, in-ground gunite
    Pressure DE filter
    2 HP Hayward Pump
    Solar Heating System

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    Re: Very Low FC, Very High CC

    Congratulations on finishing your SLAM.
    Lisa
    Intex AG vinyl 15' x 48" 4,300 gallons due to skimmer install, Krystal Clear SF pump combo 2800 GPH, Krystal Clear SWG, Pool Blaster Max vacuum, Hayward thru the wall skimmer, TF 100 test kit with speed stir, K 1766 Taylor salt test, My SLAM Process

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