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Thread: Shocking a spa

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    Shocking a spa

    I am reading up on all your helpful info. I understand I need to shock a hot tub 1x a week ?..i'm going with the Bleach I shock with bleach or MPS ?..and what is Mps. thank you

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    dmanb2b's Avatar
    Join Date
    Apr 2009

    Re: Shocking a spa

    Hi Jojo, welcome to TFP.

    Here is a discussion under the further reading section in Pool School (Button on upper right of this page). I'm pretty sure you use chlorine or MPS to shock weekly and oxidize any bather waste.


    Monopersulfate (aka MPS) is a non-chlorine shock
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    Join Date
    Mar 2007
    San Rafael, CA USA

    Re: Shocking a spa

    If you are going to use the Dichlor-then-bleach method, then there should not be any need for regular shocking if you are using sufficient chlorine after each soak to handle bather waste. It's similar to a pool in that regard -- very few of the tens of thousands of people using the BBB method for pools shock their pools regularly. The shocking referred to in the Pool School article is optional and only needed if you find it necessary. Most people using Dichlor-then-bleach do not shock. They are also able to have the water last about twice as long as those using Dichlor-only and the water quality at the end of that time is still superior, but the water needs to be changed due to the increase in chlorine demand (and salt levels that get higher -- some spas are not designed to handle higher salt levels).

    The rough rule-of-thumb with a hot (104ºF) spa that does not have an ozonator is that every person-hour of soaking requires around 3-1/2 teaspoons of Dichlor or 5 fluid ounces of 6% bleach or 7 teaspoons of non-chlorine shock (43% MPS) to oxidize bather waste. You'll know you are using enough oxidizer (chlorine or MPS) if you consistently have a measurable FC at the start of your soak. For those who want to soak with less chlorine, target 1-2 ppm FC as the level of chlorine you want remaining at the start of your soak and then add sufficient chlorine right after your soak to handle the bather load (i.e. person-hours of soaking). If you have an ozonator and use the spa daily, then the oxidizer demand amounts will be roughly half as much as indicated.

    On the other hand, if you use the Nature2 with MPS method, then regular shocking with chlorine is usually required since MPS is not always sufficient to oxidize all bather waste as effectively as chlorine. The main advantage to this method is avoidance of chlorinated disinfection by-products and not having any noticeable chlorine smell (though with Dichlor-then-bleach, starting a soak with 1-2 ppm FC minimizes the chlorine smell).
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    Re: Shocking a spa

    Thank you for thr great info on here.

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