Chlorine and Non-chlorine shock

tnthudson

LifeTime Supporter
Mar 31, 2008
353
Central VA
Hello,
I have a Hot Springs spa and am refilling it today. We have an ozonator and also silver ion, but above that I do use chlorine (Sodium Dichlor) and 'Spa Oxidizing Shock' (non-chlorine, contains potassium monopersulfate). We've always been told to add the chlorine and the potassium mono. at start-up, but I'm wondering if they should be added together? Or should there be a period of time between the adding of the two?
And subsequently, when we test, would we add chlorine (if needed) and potassium mono. together?
 

chem geek

TFP Expert
LifeTime Supporter
Mar 28, 2007
12,083
San Rafael, CA USA
It's completely up to you how much you add of each and there is no problem having both in the water at the same time. With the silver ions in the water, even the non-chlorine shock (MPS) is acting like a sanitizer so basically both the MPS and the chlorine are sanitizers as well as oxidizers. Roughly speaking, it takes twice as much volume of MPS (if it's 43% MPS product) as Dichlor for equivalent oxidation (Nature2 says it's 3 times, but they've got the density wrong).

As for disinfection, the trick will be either to have some measurable FC from the chlorine OR have a higher CC level from the MPS (or a separate MPS measurement if you can do that via the MPS interference remover for the FAS-DPD test or a separate MPS-specific test strip). The disinfection level of MPS recommended by Nature2 (which has silver ions) is equivalent to about 4 ppm FC though will measure as 4 ppm CC except for immediately after adding it (it can bleed through somewhat to FC right after adding it due to some contaminants).
 

tnthudson

LifeTime Supporter
Mar 31, 2008
353
Central VA
Cool! Thanks again Chem Geek. BTW, I measured my pH before draining my hot tub (due to my wife breaking out) and it was 8.2 plus. I really blew it this time, going to watch it much better now. Thanks again for your help!
 
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