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Thread: Which CYA Level to Shock at 40 or 50?

  1. Back To Top    #1

    Join Date
    Mar 2015
    Cleveland, Ohio

    Which CYA Level to Shock at 40 or 50?

    Yesterday, I finally got my CYA levels up to 40, which means I was able to get my FC levels up to 16 to do the SLAM process to clear up my cloudy pool water. Water is looking clearer, but still not crystal, so I'm thinking just stay with it until I see the results I want.

    One question. A few times, when I repeated the test (kit said you could dump the water from the CYA View Tube back into the CYA Mixing Bottle and pour in again) it looked like I might be closer to 50. So, basically, I'm getting readings between 40-50 now. I know the test isn't totally on the nose accurate and it's subjective, but given that, is it better to shock at the higher level. Should I bring my FC level up to 20 to try to clear the pool just in case the CYA level really is 50 or is it better to go with the lower number 40 and shock at that level?

    Just bought first above-ground pool!
    24' x 54" round Matrix by Sharkline
    150 sq. ft. Pentair cartridge filter with 1 1/2 HP dual speed pump
    Looking into heaters now...
    Any help is appreciated!

  2. Back To Top    #2
    mikemass's Avatar
    Join Date
    Jul 2013
    Northern Howell, NJ

    Re: Which CYA Level to Shock at 40 or 50?

    If in doubt, shock at the 50 level. Extra bleach not going to hurt anything aside from a few extra bucks spent.
    25 + year pool owner. Current pool (going on 11th year) - 38K gallon in ground Gunite/White Plaster, Spillover Spa, Hayward Cartridge Filter, Hayward 450k BTU NG Heater, Hayward Goldline Aqua Logic control with T-Cell-15 Salt Water Cell, Dolphin Explorer.
    You Need: Bleach, a A Test Kit & a Bookmark to "Pool School". Now what's your question?

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