What Happens If You Shock Too Much? - Hot Tub Water Chemistry - Pool and Spa Forum

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What Happens If You Shock Too Much?


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#1 Whoneedsavacation

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Posted 22 April 2008 - 01:41 PM

How do you know if you are using too much MPS or using it too often? What will happen if you do so? We use our bromine-sanitized tub 3-5 times a week, typically, and I shock after each use with MPS. I'll also make sure it is shocked at least once a week if we are out of town or something like that. I'm a bit casual with the shock, I throw in probably 2-5 TBL using the cap from the jar. What kind of trouble can I get into this way?

#2 chem geek

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Posted 22 April 2008 - 03:01 PM

When you shock with MPS, it will first oxidize any organics in the water (urea/ammonia, mostly) and then will re-activate bromine (from bromide) so you can rather easily tell if you are using too little or too much by measuring your bromine level. If your bromine level gets to zero or close to zero at any time, then you aren't using enough MPS. If your bromine level remains too high (say, over 8 ppm consistently), then you are using too much MPS. This assumes that you have some sort of bromide bank to begin with (i.e. that you added sodium bromide initially in addition to using your bromine feeder).

Roughly speaking, 1 tablespoon of MPS is roughly equivalent to 1 teaspoon of Dichlor in terms of oxidizing power and in 350 gallons this is roughly equivalent to 2 ppm FC. The amount of urea/ammonia from sweat can consume up to 7 ppm FC per person-hour of soaking so would be roughly 3.5 tablespoons of MPS per person-hour. So if there are two of you and you soak for around one-half hour most days, then you might be a little on the high side of MPS usage. Just check your bromine level as that's the easiest way to know for sure.

Richard




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