Sodium Sulfite or sodium thiosulphate in hot tub??? Yes or No to bring down FC?

duganderson

Well-known member
Jan 26, 2021
70
Minneapolis
I just treated my hot tub with Ahh-Some before draining and refilling. I shocked with 2.5 T. diclor per directions with Nature2 for my 400 G spa and the chlorine level is still above 10 PPM FC after 14 hours. The cover is off. I'm getting impatient and curious about any negatives with using Sodium Sulfite or sodium thiosulphate to bring down the chlorine?
 

YippeeSkippy

Mod Squad
LifeTime Supporter
Jan 17, 2012
15,619
Evans, Georgia
curious about any negatives with using Sodium Sulfite or sodium thiosulphate

Cost? Use Hydrogen Peroxide to lower FC. Its cheaper, I'm sure.

<looking for formula.... I've forgotten how much> Be right back!
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
23,986
Northern NJ
Pool Size
35000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-60
How_Can_Free_Chlorine_be_Lowered_in_Pool_Water.

Hydrogen Peroxide – use 1 gallon of Aqua Silk Oxidizer per 10,000 gallons of pool water to lower chlorine level by 55 ppm. For spas, use 3% drug store peroxide, 2 ounces per 100 gallons of spa water, to lower chlorine (or bromine) level by about 10 ppm.
 

YippeeSkippy

Mod Squad
LifeTime Supporter
Jan 17, 2012
15,619
Evans, Georgia
One chemistry expert ChemGeek says this:
Or you can use hydrogen peroxide to lower it faster. You use the same amount of 3% hydrogen peroxide as the volume of 6% bleach in terms of FC -- that is, figure out the FC you want to drop, look up how much 6% bleach that would be (pretending you wanted to raise the FC by that amount), and then add that volume of 3% hydrogen peroxide to the spa to lower the FC.
 
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duganderson

Well-known member
Jan 26, 2021
70
Minneapolis
GREAT! Thanks! How quickly after adding hydrogen peroxide can you safely use the hot tub? (assuming the FC is 3 or lower)?

Also, curious if there are any negatives to using hydrogen peroxide (buildup of TDS, damage to hot tub, etc.) when Chlorine is too high?
 
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