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Thread: Chlorinating Using Shock Instead of Tabs

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    Chlorinating Using Shock Instead of Tabs

    My pool is 16í x 32í with a deep end (approximately 20,000 gals.). I have been using Samís Club Sanitizer-Shock-Stabilizer (Dichloro-s-triazenetrione-hydrated) for shock every week. I also use this for chlorine by adding about one cup every 2 or 3 days. Would I be better off using Samís Tablets (trichloro-s-triazinetrion)? The tablets are much more expensive than the shock.
    16' x 32' vinyl with 8' deep end, appx. 21K gals, 1 hp Water Ace pump, Hayward Vari Flow 75gpm sand filter, 3 returns, 2 skimmers, 2 main drains, Dirt Devil robotic cleaner.

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    Mod Squad Bama Rambler's Avatar
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    Re: Chlorinating Using Shock Instead of Tabs

    Welcome to TFP.

    You'll be much better off getting a good test kit and using liquid chlorine (aka bleach) for regualr maintenance. It's cheaper than either Dichlor or Trichlor, and it doesn't constantly add CYA to your pool shich both of the others do.
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/ľhp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
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    Re: Chlorinating Using Shock Instead of Tabs

    I already have about 100# of the shock-sanitizer. This should last me the rest of the season. In a pool that size (20K gallons), how much bleach would you use a week?
    16' x 32' vinyl with 8' deep end, appx. 21K gals, 1 hp Water Ace pump, Hayward Vari Flow 75gpm sand filter, 3 returns, 2 skimmers, 2 main drains, Dirt Devil robotic cleaner.

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    Mod Squad jblizzle's Avatar
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    Re: Chlorinating Using Shock Instead of Tabs

    Welcome

    I recommend you read through Pool School (button at upper right of page) a few times to start getting a better idea about your pools chemistry.

    As stated before, the dichlor and trichlor both add stabilizer (CYA) along with the chlorine (FC). The FC is used up, the CYA builds up. The amount of FC you need in the pool is a function of the CYA level (see chart in Pool School). Soon the CYA level will get to a point that the powder and tablets will not be able to adequately maintain a high enough FC level and the pool will turn green.

    For example, we recommend a CYA level of 30-50ppm. The 100 pounds of dichlor you have will add 300ppm of CYA!!!

    The only way to lower the CYA level is through draining and replacing water in the pool ... we try to avoid this and thus recommend the use of liquid chlorine ... which in general is actually cheaper for the amount of FC ppm added to the pool.

    Again, read Pool School and then ask questions about anything you do not understand.
    Jason, TFP Moderator
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    Mod Squad jblizzle's Avatar
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    Re: Chlorinating Using Shock Instead of Tabs

    To address your question, a "normal" clean pool looses 2-3ppm of FC every day to the sun and organics in the summer. In a 20k gallon pool, you would need about 100oz of 6% bleach everyday ... so about 5.5 gallons per week.

    Using dichlor, you would need need about 1.5 cups (12 oz) daily to add 2.5ppm FC, this will also add 2.3ppm CYA. So in 1 weeks time, you will have raised your CYA by 16ppm.

    This is NOT the appropriate use of dichlor. Trichlor adds less CYA, but it still builds up.

    Oh, and I forgot to mention in my previous post, These powders and tablets are VERY acidic, so they can quickly lower the pH and TA below recommended levels if you do not do something to maintain the pH.
    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: Chlorinating Using Shock Instead of Tabs

    My pool is a bit bigger and I use one 3 jug case of Clorox per week in the heat of the summer. I add 1 big 182 oz jug of 6% bleach every other day (or 5.2 gallons per week). Cost about $8. I have recently switched to 10% Liquid Shock from the pool store and it seems that I am using less on a dollar cost basis, I have not been back from vacation long enough to be certain. Once temperatures are less than 95 - 100 degrees, the chlorine usage goes down.

    However, your pool will be different. How different will depend on all sorts of things; first the level of stabilizer in the pool now, whether you have some algae now, how much sunlight, agitation (fountains, waterfalls, cannonballs, etc), swimmers, whether they lather on the sunscreen and hair products, if they shower first, dogs in pool, how clean you keep the skimmers and floor of the pool...... all this and more play into chlorine usage. I have a medium-high agitation from spillover spa, low usage, high leaf and dirt levels from trees and landscape, sun but a lot of shade as well.

    I will point out that I also do use trichlor tablets from time to time, when I go on vacation. Because that adds stabilizer (CYA) I am very careful about how much I use of that. Only when CYA is at the low end of the range. Never when it is above 45 ppm. I also use cal-hypo from time to time, when my CH is low. It is even cheaper than bleach, if you need the CH. Trichlor is cheaper than bleach, if you need the CYA. Liquid Shock is a bit cheaper than bleach, if your pool store carries it at a good price. Bleach is cheaper than all of the above if you do not need the CH or the CYA because by avoiding the build up of CYA you avoid having to drain and refill the pool and add back the correct chemicals to balance it (maybe CH, maybe metals from well water, maybe acid to correct pH and TA issues). Most of all, if you keep the CYA and the chlorine in line, you avoid things like Clarifiers, 'algae destroyers', flocculants, and all the other junk the pool store seems to want to throw at pool owners.
    23,000 gallon in ground pool with rock waterfall and spillover spa, Aqualink control system, Polaris 380 cleaner, Purex Triton Clean&Clear Plus cartridge filter. Located in The Woodlands, Texas.

    Pool owner since Nov 2008, Trouble Free since April 2009. Happy to help when I can.

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    Re: Chlorinating Using Shock Instead of Tabs

    ^^^^^Great post. This is exactly how I manage mine. It's probably confusing to someone just starting out, but this is where you get to when you understand how all the various sources of chlorine affect your water chemistry and you have good test info to go with it. I use mostly LC in 2.5 gal carboys, but I'll switch to bleach if it ever gets to be cheaper--hasn't happened yet. I always have tabs (for vacation/travel) and cal-hypo on hand to use when I need it. My fill is low CH and I need to add Ca from time-to-time.
    Current: 28,000G 18'x36' I/G AnthonySylvan Plaster; Waterway 60 sq.ft. DE Filter; 1.0hp x 1.65 SF Two-Speed (B2982) WhisperFlo; 2004-Present
    Previous: 40,000G 20'x40' I/G Koven unlined WWII salvage 5/8" marine steel; Lomart Stainless Sand Filter; 3/4hp Hayward SuperPump; 1946-2003 (managed by me from about 1964)
    Ancient Taylor K-2000, upgraded with Taylor CH, TA, and FAS-DPD, and TFT CYA tests.

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    Re: Chlorinating Using Shock Instead of Tabs

    Quote Originally Posted by Larry65
    I already have about 100# of the shock-sanitizer. This should last me the rest of the season. In a pool that size (20K gallons), how much bleach would you use a week?
    It depends on where you live, but expect to use 2-3ppm per day. In a 20K gallon pool if you are using 3ppm per day, the pool calculator says you will nee 124 oz per day or 7 gallons per week. Around here a gallon costs 2.50 so around $15/week of bleach.
    17,800 gallon, IG pool, 595 sq feet (17x35x4.5 avg rectangle), Hayward 525 cartridge filter, diamondbrite, 2 hp 2 speed hayward tristar filter, Stenner 45mhp10 automatically chlorinating

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