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Thread: Help understanding shock level

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    Help understanding shock level

    Split by moderator from HERE. Please ask questions in your own thread. Thanks, jblizzle

    Ok...I'm a newbie at this method. I came to this sight in desperation since my hubby said if we have one more summer with this many times of green water the pool will be bulldozed!
    I have been reading threads for 5 days as I'm also trying to clean up our pool. My good test kit is scheduled to arrive today but I have been using distilled water to dilute my water to get an idea of my FC levels...thanks to advice from this forum!
    My last CYA test from a local pool store was 96 so according to the CYA/chlorine chart my target shock level is around 37. (I chose to not do a drain and refill since we are 6 wks from closing)

    Now my question is this....if your CYA is 50...the chart indicates a target shock level of 20. But after watching your progress...your FC levels were below that most of the time...and you were clear in 4 days? I'm trying to figure out if I'm over chlorinating while trying to kill algae!
    Julie
    33' AGP, 26k gal
    26" Eco kleer sand filter, 1.5 HP pump

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    techguy's Avatar
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    Re: Oops! I forgot my pool! (A photo series)

    Jann, you should have started your own topic since you have your questions.

    Ovr chlorinating is a relative concept. If your pool had a 50CYA, you would need 20FC to SLAM to pool and this 20FC needs to be maintained until the pool clear. It may require hourly additions of liquid chlorine to keep it there. With your near 100CYA, you need to bring the FC to 39FC, AND maintain this level until the pool is clear. This is why we speak of the CYA being critical.

    Over chlorinate: Since the free chlorine binds with the CYA, it buffers the effect the chlorine has on the swimmers, and on the algae and other debris. This CYA buffering is why it requires so much more chlorine in the pool. The chlorine is still there, it's just not immediately available to kill algae and it's not damaging or irritating to the pool or swimmers.
    -- Guy --
    10K gallons in 21' Round 52 inch wall Aqualeader AG, Hayward Power Flow LX 1.5 HP pump motor, Hayward Perflex EC50AC DE filter w/Cellulose, Wide mouth skimmer, 2013 new Diver Dan (craigslist) to replace the faded old Hayward AquaBug. TF-100

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    Mod Squad jblizzle's Avatar
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    Re: Help understanding shock level

    I am just going to point out as well that the while the shock level for 50ppm is 20ppm in Pool School chart, if you are using the poolcalculator.com, the FC shock level is listed as 16ppm. Either will work, but the chart is more aggressive.
    Jason, TFP Moderator
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    Re: Help understanding shock level

    Sorry for not starting my own thread...now I know

    So..I need to maintain shock level until my pool is crystal clear? I'm milky blue right now and can barely see my brush at the bottom. Just asking since I've been through 50 bottles of bleach already and on day 4
    Julie
    33' AGP, 26k gal
    26" Eco kleer sand filter, 1.5 HP pump

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    Mod Squad jblizzle's Avatar
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    Re: Help understanding shock level

    Correct, keep SLAMing ... 50 bottles and only 4 days is no where near a record ... and now you are seeing why we recommend lowering the CYA first.

    Are you seeing CC? Have you tried the OCLT?
    Is the filter pressure rising? Are you backwashing when it goes up 20-25% over the clean pressure?
    When was the last time you inspected/cleaned the sand?: my-sand-is-channeled-how-to-fix-it-t7626.html#p60821

    You could try some DE in the filter to see if that helps clear the cloudiness: pool-school/add_de_to_a_sand_filter
    Jason, TFP Moderator
    18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
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    Re: Help understanding shock level

    By the way... if you have added 50 bottles and your pool is milky blue and you can see your brush... you are doing a GREAT job!! You should be done pretty soon and your chlorine consumption will taper off as you get closer to clear.
    -- Guy --
    10K gallons in 21' Round 52 inch wall Aqualeader AG, Hayward Power Flow LX 1.5 HP pump motor, Hayward Perflex EC50AC DE filter w/Cellulose, Wide mouth skimmer, 2013 new Diver Dan (craigslist) to replace the faded old Hayward AquaBug. TF-100

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    Re: Help understanding shock level

    Jann,

    I was in your shoes a week ago. My pool is FINALLY clearing up, it is no longer green but a cloudy blue. Two more days I think. I want to point out NOT to trust the pool stores reading on your CYA. They told me mine was 90+ I couldn't believe it. It is a really hard test to read. I had the guy do it again and I read it, I was getting about 50 on their kit. If I had believed them I would have had more problems, and wasted a lot of chlorine. Thankfully my kit was delivered while I was out, so I learned how to use it and did the CYA test immediately. The Taylor 2006 is much more reliable, and my CYA is 30!!!

    I am fast becoming a true follower of TroubleFreePools and BBB. Good luck, it sounds confusing but with a good kit, diligence, and patience it will be usable in a few days.... maybe even for Labor Day!!
    Amanda

    30,000 gl; IG Vinyl; Hayward s210s sand filter; 1HP pump;Zodiak exp. Nature2; Oct 2006;

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    Re: Help understanding shock level

    To be truthful 300 is 90+, just a little more plus than you thought. This is why we don't trust pool stores very much. They frequently tell the "truth", just not accurately. They focus on the attribute of the test that sells the most product. Like PhosFree that focuses on the "algae food" phosphate, not actually killing the algae.

    For example: They tell you need need an FC of 1-3... over the minimum required for your CYA... that they don't feel important enough to tell you, or accurately measure.
    -- Guy --
    10K gallons in 21' Round 52 inch wall Aqualeader AG, Hayward Power Flow LX 1.5 HP pump motor, Hayward Perflex EC50AC DE filter w/Cellulose, Wide mouth skimmer, 2013 new Diver Dan (craigslist) to replace the faded old Hayward AquaBug. TF-100

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    Re: Help understanding shock level

    Thank you for the encouragement! Really needed that today!

    Funny thing is that I'm not seeing much rise in pressure. I put new sand in this spring. I did backwash last night but did not see hardly any brown water coming out. I will try the overflow method and look into DE.

    My Taylor 2006 test kit is scheduled to arrive today so hopefully I can get my tests ran. I can smell chlorine when I lean down to the water but its not overpowering. I have been testing morning night and almost every hour during the day. I have not passed an OCLT.
    Julie
    33' AGP, 26k gal
    26" Eco kleer sand filter, 1.5 HP pump

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    Re: Help understanding shock level

    If it smells like chlorine in the laundry room, that is a good thing.

    If it smells like the "pool chlorine" of a hotel pool, that means you are killing algae and the sun needs to drive of the "CC" combined chlorine that is partially oxidized waste/chlorine (the stinky chlorine smell). If this is more like it, this means you need to keep slamming! Your test will tell you when you get it.
    -- Guy --
    10K gallons in 21' Round 52 inch wall Aqualeader AG, Hayward Power Flow LX 1.5 HP pump motor, Hayward Perflex EC50AC DE filter w/Cellulose, Wide mouth skimmer, 2013 new Diver Dan (craigslist) to replace the faded old Hayward AquaBug. TF-100

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    Re: Help understanding shock level

    I would say it smells like the laundry room and my test results indicate no CC

    Here are my test results,

    FC 45
    CC 0
    CYA 65 Yay!! Yes...it's high but much better than the reading of 96 from the pool store!
    Julie
    33' AGP, 26k gal
    26" Eco kleer sand filter, 1.5 HP pump

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    Re: Help understanding shock level

    With a CYA of 65, you should be SLAMing at 26. Let the FC fall to the high 20s, but don't let it get below 26. Too much chlorine can be as bad as too little.
    33' round, 23,000 gal AG vinyl , 1HP 2spd PowerFlo Matrix downsized with 3/4HP impeller (X2), Hayward S180T 150# sand filter (X2), Hayward H250 NG heater Pool Store year 1 - $850 for 2 months; Pool Store year 2 - $440 for 2 months, TFPC year 1 - $170 for 4 months; TFPC year 2 - $95 for 4.5 months
    The most important article on this site - The ABCs of Pool Water Chemistry

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    Re: Help understanding shock level

    Should I be concerned that my chlorine levels are still really high? I tested when I got home from work and my FC was 42. I am going to do an OCLT test tonight but my gut feeling is that I will pass since I only dropped 3ppm in 24 hours. My water is still blue milky/cloudy but getting clearer...could that be caused by high levels?
    Julie
    33' AGP, 26k gal
    26" Eco kleer sand filter, 1.5 HP pump

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    Smykowski's Avatar
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    Re: Help understanding shock level

    Quote Originally Posted by Jann
    My water is still blue milky/cloudy but getting clearer...could that be caused by high levels?
    The cloudy is dead algae. Keep SLAMing. In your case, keep brushing and vacuuming, but you won't have to add any chlorine until your FC gets down to the mid-20s.

    If you pass the OCLT (which you may), that means that there is no more algae living in the pool consuming the chlorine. Now it's a matter of waiting for the filter to trap the dead algae which will clear the water. We strongly recommend continuing the SLAM until all three criteria are reached as an insurance policy to make absolutely sure there's nothing in there.
    33' round, 23,000 gal AG vinyl , 1HP 2spd PowerFlo Matrix downsized with 3/4HP impeller (X2), Hayward S180T 150# sand filter (X2), Hayward H250 NG heater Pool Store year 1 - $850 for 2 months; Pool Store year 2 - $440 for 2 months, TFPC year 1 - $170 for 4 months; TFPC year 2 - $95 for 4.5 months
    The most important article on this site - The ABCs of Pool Water Chemistry

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    techguy's Avatar
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    Re: Help understanding shock level

    Do you have any lights in the pool. I know its AG but sometimes people do. Also, now is a good time to give the hard pool toys, floats, tools, and other stuff a good soaking in high FC water.

    Also, have you scrubbed the backside of the ladder?
    -- Guy --
    10K gallons in 21' Round 52 inch wall Aqualeader AG, Hayward Power Flow LX 1.5 HP pump motor, Hayward Perflex EC50AC DE filter w/Cellulose, Wide mouth skimmer, 2013 new Diver Dan (craigslist) to replace the faded old Hayward AquaBug. TF-100

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