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Thread: No chlorine reading after shocking

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    No chlorine reading after shocking

    Hi guys,

    I'm new here but I did go to pool school and I have learned a lot. Still I have some questions First of all, I am from the Netherlands and thus have access to different chemicals, different tools and I am used to a different metric system. Also, not a lot of people have a pool in the Netherlands, since it rains 360 days a year Kidding but with luck we have 2/3 months in which we can use the pool on good days. This means that there is not a lot of information to find on problems which are a bit more difficult to defeat, other than: alkalinity is low or high, ph is low or high etc.

    Especially not on the problem we encounterd. That is what I found here and this website + very good local pool dealer saved me from simply draining the **** pool.

    Last year we bought a house and it had a pool, fulfilling a dream 10yrs earlier than expected. We had no clue what to do with the pool and let the company who installed it advise us. He advised us to keep it closed, make sure it was heated when the temp was below 0 celcius and leave it alone. Mistake 1. He also helped us start the pool back up, measuring was not needed he said. Mistake 2. Of course the water was a dark shade of green. He seemed to know by heart that the PH needed a rise and advised us to add a chlorine shock. Which did not work, plus I did not measure any chlorine with a simple DPD test the previous owner left behind.

    So I went in and read all I could on the internet regarding pools (which I should have done in the first place) and purchased a test kit. We do not have the advanced test kits like you guys have. At least, not being a pool specialist, you don't. Other digital tests we do have are expensive and limited to FC, CC, Alk and PH. I might pick one up while I'm in the US in a few months. So I did a test with a strip and PH was ok but Alkalinity was only 40, CYA 30/40. No chlorine.

    I bought TA+, got the TA up to at least 120ppm. I tried another shock, didn't work either and no reading again, not even after 30 minutes. I did this a few times, with different types of dichlor. (I began to think that he sold be washing powder which just smelled like chlorine). My teststrip did read chlorine after swiping the bucket I used to divide it over the water so I was sure it wasn't bleached by the chlorine.

    So, a lot of euro's wasted, no chlorine reading and still a green pool. I drained 1/3 of water from the pool, shocked it, used anti-algue gel (I'm not sure you are familair with this but it gives you a small layer on the sand filter and it consumes fosfates) and I added tabs which bind the small debris (don't know how you call it). The gel catches the debris on the filter and after you had enough, you simply backwash. That at least got me a somewhat clear but still green pool. No clorine reading.

    I started searching on English websites and found this one. Plus some topics from people with the same problem as I did. This was very interesting: http://www.troublefreepool.com/conte...tain-shockingl Though I have the handicap of not having a good test kit, I decided to try this. I got 25 liters of liquid chlorine, 13,8 percent and used 6 liters this morning. Which should have been enough for 20ppm. First time I got a purple test reading after an hour I continued testing with the strips which only go till 10ppm. I decided that when it would drop, I would add another 3 liters. After 6 hours, my pool was clear! Gone was the green water and crystal clear water appeared. I was (and am) ecstatic.

    So, this evening, about 9hrs after the shock, I saw that the chlorine reading drop under the 10 but above 5. The sun was on the pool most of the day so I can imagine that it burned off some of the chlorine. I cannot use the cover at the moment as it would discolor from the chlorine level.

    I took pictures after every test, so I could follow the discoloring of the strip somewhat better. I realize it is still guesswork but hey, a woman can try and at least, now it's clear. So after seeing it drop, I added another 3 liters and brought it back above 10ppm again.

    First I want to thank you for providing the info. Otherwise my morning would have existed of draining the pool and the next few days of filling it. I hope to get there with the limited tests I can do at the moment. The new company I have found to help me with my pool is too far away to have it tested every day.

    So that is a lot of background information but after reading previous topics I kind of have the idea of the suggestions you would give me so you need to know what I did already and why I don't have a good test kit.

    I do have some questions. The slam guide says that I am done when I have a clear pool and my chlorine level does not drop with more that 1ppm overnight. But isn't liquid chlorine supposed to drop fast (in a few days) after shocking? I mean, I always understood that I should have about 2ppm reading for normal pool use and after shocking the ppm should drop within a few days back to normal because you use a fast working chlorine.

    So it would be natural to have it drop a few ppm in a day right?

    Next, how can I best prevent this next summer?

    By the way, the pool is 8metersx4meters, 45.000 liters with a sand filter.

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    Patrick_B's Avatar
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    Re: No chlorine reading after shocking

    Welcome! Glad you found us!!

    The over night loss of 1.0 is to see if something besides the Sun is getting your free chlorine. Like, organics in the pool. You test after Sundown, and again before sunrise to find out. Not all day over the course of 24 hours. Our shock procedure is sustained until all those criteria you read about are met. Not having the proper kit for FC testing makes it impossible to follow our method precisely. What are you testing with now?

    Sorry, but yes over the course of a day 2-4 PPM FC loss is normal.
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  3. Back To Top    #3

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    Re: No chlorine reading after shocking

    I realize that but I have to make due I am using Aquachek yellow strips. The only ones I can buy here which give you the stabilizers as well.

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    Patrick_B's Avatar
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    Re: No chlorine reading after shocking

    Well, you have to do what you have to do. Understand you there. I would encourage you to look around for some type of full kit if you can get one. Strips are very unreliable, so even a basic kit woul be nice for chlorine and pH.
    TFP Moderator
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    Mod Squad jblizzle's Avatar
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    Re: No chlorine reading after shocking

    Welcome to TFP!!!

    Please add your location (City, State or City, Country) to your profile and pool details to your signature as described HERE as it will help us help you.

    I have to agree, a better test kit is essential to pool maintenance.
    Jason, TFP Moderator
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  6. Back To Top    #6

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    Re: No chlorine reading after shocking

    Also, I noticed you mentioned buying TA+ and adding it to the pool---just so you are aware, baking soda is the same thing for all practical purposes, so if you find you need to raise TA again, just buy that instead. The poolcalculator.com site PoolMath can give you proper measurements of how much baking soda to add to get to your target.
    Last edited by jblizzle; 05-14-2015 at 02:42 PM. Reason: We recommend PoolMath now
    17.4k gallon IG pool with attached spa (spa itself is 730gal), Super Blue Diamondbrite plaster, Circupool SI-45+ SWG, BH/Hayward Cartridge Filter, 2hp 2speed Hayward Super II pump, , Jandy Valves, Waterway Skimmers, Rheem 400k Heater, Polaris 360 cleaner, built 2000+-, replastered June 2015, TF-100 kit---Here's my pool test reading history

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    Richard320's Avatar
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    Re: No chlorine reading after shocking

    Quote Originally Posted by badzeep View Post
    I do have some questions. The slam guide says that I am done when I have a clear pool and my chlorine level does not drop with more that 1ppm overnight. But isn't liquid chlorine supposed to drop fast (in a few days) after shocking? I mean, I always understood that I should have about 2ppm reading for normal pool use and after shocking the ppm should drop within a few days back to normal because you use a fast working chlorine.
    When it says overnight, that's exactly what it means. Overnight. Not 24 hours. Only two things consume chlorine: UV rays from the sun, and organics, which include algae.

    So... you test it after the sun goes down and test it again before the sun comes up. With no sunlight losses, any losses you see will therefore have to be from organics. No alage and no sunlight means no chlorine loss.

    You've got it rough because you can't get a FAS-DPD test kit that measures super accurately.
    So it would be natural to have it drop a few ppm in a day right?
    Yes, due to sunlight.
    Next, how can I best prevent this next summer?

    By the way, the pool is 8metersx4meters, 45.000 liters with a sand filter.
    Close the pool as late in the season as you can and open as early as you can. Algae doesn't grow much in cold temperatures. You could also start hunting now for Polyquat 60 algaecide to put in at the end of the season. I have no clue if it's even legal in the EU, which is why you want to start hunting now.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
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    Re: No chlorine reading after shocking

    Thanks! I'll test tomorrow morning and see how it held. When in doubt, I'll slam it again.

    I could probably get the digital aquachek for a good price. Would that be a good tester?

    Thanks for the baking soda tip! Baking soda is about 11 euros per kilo, ta+ I can buy a 3kg bucket for 25 euro here in NL. If I find baking soda cheaper, I'll get it for sure! The 25l liquid chlorine was 15 euro. Felt like a bargain, compared to the dichlor which is 85 per 3kg.

    I will add the info to my signature, just need to retrieve some info still

  9. Back To Top    #9

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    Re: No chlorine reading after shocking

    Thanks Richard. They sell a fluid for winter in Belgium. No idea what chemicals it contains but I'll check.

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    Mod Squad jblizzle's Avatar
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    Re: No chlorine reading after shocking

    We generally are not a fan of the digital testers either. They usually have limitations, like 10ppm for FC (which is not helpful for a SLAM), and you have to keep them calibrated, and you just never know if the answer is bogus.

    Have you discovered Pool School yet? Start with these. The 2nd one tells you the grocery store equivalent to all the pool store chemicals
    ABCs of Water Chemistry
    Recommended Pool Chemicals
    How to Chlorinate Your Pool
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    Re: No chlorine reading after shocking

    Check out the Pool School article on Closing In Ground Pool or Closing Above Ground Pool
    Joel - TFP Moderator - Minnesota - **Become a TFP Supporter!** Helpful Links: ABCs of Pool Water Chemistry - SLAM Procedure - Chlorine/CYA Chart
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