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Thread: Do Chlorine Tablets (Trichlor) Expire?

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    Do Chlorine Tablets (Trichlor) Expire?

    I stopped using the tablets a few years ago when I switched to a SWG, but I still have a nearly-full bucket of tablets. I just had the pool replastered about five weeks ago and have the water in ideal balance, except for the chlorine. I haven't added the salt, yet, so I've been using bleach and a floater trying to keep the level around 3 ppm.

    The problem I'm having is that I need to add about 1.5 quarts of bleach to the pool each day to maintain the level, in spite of the floater. The floater is kept right over the drain (center of deep end) with its vents open fully. It is in the stream of the pool's strongest return to the point that small eddies form on the 'downstream' side of it when the pump is running. There are four three-inch tablets in it and it smells of chlorine when opened. Still, it's not keeping the FC up.

    Here are my current numbers:
    FC: 3
    CC: 0
    pH: 7.2
    CYA: 40
    TA: 100
    CH: 225
    Temp: 68 F

    Water is sparkling clear. I will double my CYA before I add the salt for the SWG. I will add the CYA Monday and switch to salt chlorine generation next weekend (I think). The solar will begin heating tomorrow (I just switched it on this evening).
    blubluenoiseise

    My pool: 14,750 gallons in-ground plaster
    FAFCO Solar panels (seven 4' x 12') with a Goldline automatic controller
    1/2 HP WhisperFlo filter pump, Kreepy Krauly cleaner, Cartridge Filter
    Aquarite SWG, Satisfied user of the TF-100 Test Kit

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    Mod Squad zea3's Avatar
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    Re: Do Chlorine Tablets (Trichlor) Expire?

    According to the pool calculator, 3-7 is your FC target, and 15 is the shock target. You have been trying to keep FC at 3, which means you are dropping out of your target range frequently. You may be on the verge of an algae bloom. Try running the overnight test to see if the FC holds. If the overnight test is o.k., you need to keep the FC around 7 until you get the SWG running, then you can re-calculate what the levels should be.

    As far as the tablets go, they dissolve and release chlorine very slowly. As long as the tablets stay dry and out of direct sunlight they should still be o.k.
    TFP Moderator
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    Butterfly's Avatar
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    Re: Do Chlorine Tablets (Trichlor) Expire?

    The tablets will probably degrade with time, esp depending on the storing/handling.

    Doing the overnight FC loss test sounds like a good idea. If you do have a problem, much better to find out now rather than after you add the extra CYA.
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    JasonLion's Avatar
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    Re: Do Chlorine Tablets (Trichlor) Expire?

    Trichlor will last a good long time if it is kept dry and cool. If it gets wet or is stored at high temperatures it will degrade. Water can ruin it quickly. Heat degrades it slowly.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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    Re: Do Chlorine Tablets (Trichlor) Expire?

    Four tabs works great in my pool (when I use trichlor), your pool is smaller and I would expect it to be fine. Your excessive chlorine demand could indicate a low-level algae problem. I recommend you do an Overnight FC Test which will require taking out the floater. If you have a low-level algae problem, this test will show it, and that will mean you need to shock.
    --paulr
    BBB "Intermediate Swimmer"
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    Re: Do Chlorine Tablets (Trichlor) Expire?

    I tested the FC last night (~3) and again this morning and found it did not appear to lose any during the night. In fact, it almost looked like I had more chlorine this morning, but I blame this on the subjective nature of the color matching on my simple test. I removed the floater during the night, so there should not have been any other source of chlorine.

    Strange!

    Is it OK to shock the pool now that the plaster is over 30 days old? Is it a good time to add salt and get the SWG running again, or should I give it more time?

    Thanks, folks!
    blubluenoiseise

    My pool: 14,750 gallons in-ground plaster
    FAFCO Solar panels (seven 4' x 12') with a Goldline automatic controller
    1/2 HP WhisperFlo filter pump, Kreepy Krauly cleaner, Cartridge Filter
    Aquarite SWG, Satisfied user of the TF-100 Test Kit

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    JasonLion's Avatar
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    Re: Do Chlorine Tablets (Trichlor) Expire?

    Yes, it is fine to shock the pool and also to add salt after 30 days have passed. I don't see any reason to shock the pool just at the moment, but you can if there is some need.
    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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