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Thread: Shock or not?

  1. Back To Top    #1

    Join Date
    Oct 2009
    Baja California Sur, Mexico

    Shock or not?

    I have a SWG, pebble pool that looks great and the water is crystal clear, however..... when I test my FC & TC there is enough of a discrepancy towards the higher TC level that makes me think I should shock the pool according to my "The Pool Calculator". Basically it says that if my CC is above .5, which I believe it is, I should shock the pool based on the Pool Calculator recommendation of a shock level of 11. What I need to know is for how long? I just started adding CYA so my levels are relatively low (see below). Oh yeah, I just started using the BBB method with absolutely great results but I am still a newbie to this whole thing. I have had my pool for about three years and I have never shocked it. I have changed about 1/2 of the water once so far.

    Advice is very much appreciated.


    Pool Size: Apprx: 20,000G
    FC= 2.0, TC = almost 3 which should translate to CC being higher than .5 (time to shock?)
    pH= 7.6
    TA= 80
    CH= 280
    CYA= 20
    Salt= 3400
    Temp= 76° (pool is in Mexico)
    20,100G, pebble pool with waterfall, swim jet & integral spa. Aqua Rite SWG, (4) 8" dia. cartridge filters.

  2. Back To Top    #2
    polyvue's Avatar
    Join Date
    Aug 2009
    Sacramento, California USA

    Re: Shock or not?

    Hello Mike, Welcome to TFP

    What kind of test kit are you using to determine FC, TC etc? In spite of the clear water if the CC is definitely above .5 ppm I would shock the pool. A constant 12 ppm FC level should work in view of such a low level of CYA. Shouldn't take long to get those combined chloramines down -- maybe just a day.

    Here's an excerpt from Pool School that may prove informative:

    • 1. Measure the FC level
      2. Add enough chlorine to bring FC up to shock level
      3. Repeat steps 1 and 2 as frequently as practical, as often as once per hour, and not less than twice a day, until:
      [list:5npspmx5]a. CC is 0.5 or lower;
      b. An overnight FC loss test shows a loss of 1.0 ppm or less;
      c.And, if you don't have a FAS-DPD test kit, the water is clear
    14,555 gal in-ground 16'x29' white plaster Pool w/spa (2007); Goldline Aqua Logic AQL-PS-8 control w/Aqua Cell 15 Salt Water Chlorination (SWCG); Hayward TriStar 1HP (1.85 SF) main / 1.5HP (1.60 SF) spa pumps; Hayward Swimclear cart filter C4025, ColorLogic LED lights; Tankless SP-18-4 electric heater; Polaris 280 cleaner.
    View of spiral galaxy in Ursa Major NGC6217 - Hubble Telescope 2009

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