What kind of chlorine do I use with high cyanuric acid?

PSC Ep. 78: What kind of chlorine do I use with high cyanuric acid?

16 thoughts on “PSC Ep. 78: What kind of chlorine do I use with high cyanuric acid?

  1. Hello all well. If cyanuric acid (CyA) is high and this elevation causes blockage of chlorine, how will I make a superchlorination using the same chlorine derivative, ie dichloro?

  2. Suppose cya has reached 50 and i want to maintain that level. Why can’t I just switch to sodium hypochlorite and still be protected from the sun with the residual cya?

    1. You can.
      The residual is not going anywhere until you drain the pool. At 50 ppm, you’ll be fine.
      You’ll be better at 30 ppm.

    1. You will have to be vigilant about chlorine levels. CYA levels drop due backwashing or draining so you would need to compensate for that. Depends on amount of use, temp, and a few other variables.

      In short, give it a try for yourself and tell us how it works.

  3. If my pool’s CYA level has reached 300, can it be treated with chlorine shock rather than having to drain 1/2 of it and diluting it with fresh water? Having to rent a submersible pump and refill the pool is going to be pretty costly so looking for a less expensive alternative.

    1. I guess in theory you can try to keep CYA at 300 and dose it with shock. But I imagine the amount of money spent on shock and unstabilized chlorine would quickly outweigh the amount to rent a submersible pump.

      The CYA shouldn’t be above 100.

  4. I live in SW Fl and have a 12,000 gallon above ground pool. We have had a very hot, dry spring after a few bouts of cold ( for us ) weather followed by fast heat ups. I have had intermittent algae problems which is handled well with normal chlorine applications. My alkalinity and ph stays in the proper ranges. I do get organic debris from a tree but I clean the pool frequently to remove it. Now my CYA level is really up and I’ll probably have to drain water off. I do not use tabs or CYA products at all. Do you think my liquid chlorine
    that I buy at the pool store could be causing part
    of the problem? I would like to avoid this problem in the future so any thoughts would be helpful. Thanks.

  5. If my CYA between 200- 300 what shock would you dose it with to lower they CYA.
    We use 3″ Chlorine Tabs • 99% Trichloro-s-trianzinetrione (Tri-Chlor) Active Ingredient
    I’m not sure if they have stabilizer included in the ingredients, should we be using those?
    Is there any other reason our CYA would be high, maybe from organic debris or any ideas?

    1. Shock doesn’t lower CYA, only draining the pool water and filling with fresh will work. Your CYA is way too high and should not be above 100.

      CYA gets in the pool because you are either adding stabilizer or the tablets or liquid chlorine contain CYA. Over the years the CYA builds up if you do not add fresh water.

        1. Doesn’t matter the pool surface type, CYA should not be that high. If you plan on draining a significant portion of your pool water, I would make sure the previous few days have had no rain, to make sure the shell does not pop out.

  6. My free chlorine and CYA levels were too high (FC around 6.5, CY over 100), so I drained about half the pool and filled it back up, but both levels were still very high (FC 3.4, CYA 70-80). A couple of questions:
    1) My pH and alkalinity are in the normal range, but my testing kit had a formula to factor in high CYA, which brought the number down to where it is too low. Should I go by the adjusted number, or with the number from my actual test?
    2) I haven’t added any chlorine in a couple of days, so the FC has dropped to normal level (2.2 as of last night), but my pool has turned completely green. If I shock it to start the process of ridding it of algae, do I start with shock? Or get the adjusted alkalinity in line first, then shock?

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