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Thread: Non-chlorine shock question

  1. Back To Top    #1

    Join Date
    Jul 2007
    Austin, TX

    Non-chlorine shock question

    After a big storm lasting a few days my pool was filled with dirt and leaves, my total chlorine was down to zero, and some algae started to grow on the sides. My numbers looked like this:

    FC 0
    TC 0
    pH 7.7
    TA 80
    CYA <20

    I have a bunch of store brand (non-BBB) pool chemicals that I want to start using. Last night I added some algaecide and some non-chlorine, potassium monopersulfate-based shock. The pool water is looking better and the algae is starting to disappear. I also added some stabilizer to get the CYA up.

    After about 24 hours my numbers are:

    FC .5
    TC .5
    pH 7.3
    TA 80
    CYA <20

    The shock freed up a tiny bit of chlorine so some FC actually registered. It's probably too soon for the stabilizer to show up however I think it or the rain this morning moved the pH down. I plan to add some baking soda to get the TA up to 100 and hopefully raise the pH a little at the same time.

    Here are my questions.

    1. How do I know when I'm done shocking and treating for the algae or when I need to add more? The shock instructions say to add 1 lb. per 10,000 gallons to destroy contaminants that have accumulated in the water and to reapply weekly to maintain water clarity. The algaecide says

    Maintenance Dosage (weekly):
    Add 4-8 oz. per 10,000 gallons.

    To Treat Existing Yellow or Green Algae:
    Add 16-24 oz. per 10,000 gallons to a pail of water and distribute.

    This implies that I'm done treating with the shock and algaecide until next week.

    2. How do I get my chlorine up? I have trichlor tabs; however the instructions say to use them after you get the pool balanced. I don't have any other chlorine products like dichlor or chlorine based shock. Should I just put some tabs in the floaters anyway or should I kick things off with some good old liquid bleach to get the ppm up to 4.0?

    Thanks, Chris
    26K IG plaster pool, 2 Baker Hydro Skimmers (Model HS), 4 return jets (one plumbed with a PoolSkim surface cleaner), Hayward 1.5 6-way Multiport Valve (Sp710x-All), Polaris 380 w/ Polaris PB4-60Q Halcyon 3/4 HP Booster Pump, Pentair SuperFlo 1.5 HP (1.65 SFHP) Two Speed Pump (SF-N2-1-1/2A), Stainless Steel Hayward vertical DE 36ft2 filter (Duralon tank model DE3600), Purex CHD Pool Star light, 2 Intermatic mechanical time switches controlling the filter pump and booster pump, Hasa 8 gallon 3/8" Pool Liquidator Chlorinator, 1.5" return line with 3 x 1.5" suction lines, Austin, TX

  2. Back To Top    #2

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    duraleigh's Avatar
    Join Date
    Apr 2007
    Sebring, Florida

    Re: Non-chlorine shock question

    Chris, I like chemgeek's criteria for clear pool water (no need to shock)
    1. CC's .5 or less
    2. Crystal water
    3. The ability to hold overnight chlorine loss to 1ppm or less.

    Generally, forget the algaecide and MSP for shocking. Fine that you used up what you had but you'll have more control shocking with Clorox.

    Assuming you've met the criteria above, I'd keep the chlorine up (remember, you must keep adding chlorine continuously to your is constantly depleted) with two things - clorox and the tabs you have on hand. The tabs will add a little CYA to the pool and give you a maintenence dose of chlorine (it will add both slowly)....stop using them when your CYA gets 35 or so.

    To get to shock level or to get immedeiate chlorine in the pool, clorox is the best. Use it when you need chlorine right you do right now. Bring your Cl up to about 4ppm or so if you've met the criteria above. If you have not, bring the Cl up to 15ppm until you do.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

  3. Back To Top    #3
    JasonLion's Avatar
    Join Date
    May 2007
    Silver Spring, MD
    You need to get some more chlorine in there right away. As long as your CYA is low trichlor tabs will work just fine. Just keep in mind that they add CYA, which will eventually get too high and cause problems unless you stop using trichlor long term. Also trichlor will lower PH. The only times you need to avoid using trichlor is when your PH or TA are way too low or your CYA is too high. You can use it right now without problems. Long term you can use bleach as a chlorine source since it doesn't add anything your don't want to the pool.

    As long as you are using trichlor tabs you should bring your TA up to between 100 and 120.

    CYA can take up to a week to disolve.

    Shocking your pool means bringing the FC level up to a specific level, depending on your CYA level, and holding it there until all the algae is dead. One application of chlorine is only occasionally enough to do it. Usually you need to add more reguarly till the algae is all completely dead.

    You should think about getting a good test kit. A good test kit is the best investment in your pool you can make. The TF Test Kit, see the link in my signature, is a good one and there are a couple of others that are also good.
    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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