# Thread: Calculator or instructions for sodium thiosulfate?

1. ## Calculator or instructions for sodium thiosulfate?

Hello!

I wanted to know if there is a calculator or instruction sheet y'all recommend for how much sodium thiosulfate to add in case my free chlorine gets out of whack again from over-zealous shocking. (it was as high as 65 before dumping in about 24 oz yesterday, dropped like a rock)

I've looked all over the internet and am finding contradictory advice, anything from 0.5 oz to about 5 oz to decrease FC by 1 ppm for a 10,000 gallon pool.

I was aiming for about 0.75 oz per 1 ppm decrease in my 2800 gallon pool as a conservative estimate.

I am grateful for any suggestions!

2. ## Re: Calculator or instructions for sodium thiosulfate?

Have you checked on the use of hydrogen peroxide? From what I have read, hydrogen peroxide neutralizing chlorine is supposed to be linear. 2.6 oz of 27% to neutralize 1 ppm of FC in 10,000 gallons.

3. ## Re: Calculator or instructions for sodium thiosulfate?

I can't find much for hydrogen peroxide except for usage in fish tanks and for industrial (read: city water) systems.

Also doesn't it depend on what kind of pool system you have (baquacil or chlorine), and how much would you need? Could drug store (3% in solution, I think) version work in a pinch when the pool store is closed or out of stock?

Stuff all over the internet about the usage of both but I can't find a set of hard numbers specifically for pool use.

4. ## Re: Calculator or instructions for sodium thiosulfate?

In the thread Best way to reduce chlorine level, I gave the following amounts to lower 1 ppm FC in 10,000 gallons:

2.6 ounces weight of sodium thiosulfate
1.5 ounces weight of sodium metabisulfite (some claim up to 3 ounces is needed)
2.4 ounces weight of sodium sulfite
2.6 cups of 3% hydrogen peroxide (2.3 fluid ounces of 27% hydrogen peroxide)

5. ## Re: Calculator or instructions for sodium thiosulfate?

Thanks, this list is fantastic! I am very grateful, because I now have options in case things go awry again!

I think one of my HTH stabilizers (CYA) contains sodium sulfite as well. Should I avoid using it and only use the "plain" stabilizer?

6. ## Re: Calculator or instructions for sodium thiosulfate?

I don't think that any cyanuric acid made for pools contains sodium sulfite. Can you double check the ingredients?

7. ## Re: Calculator or instructions for sodium thiosulfate?

You know, rather than spending a lot of time trying to figure out how to use sodium thiosulfate, you would be much better off trying to figure out how to never need to use sodium thiosulfate again. FC levels go down on their own, so normally you can just wait it out. Getting the FC level wildly too high can damage the pool and is best avoided altogether.

8. ## Re: Calculator or instructions for sodium thiosulfate?

JasonLion makes an excellent point. I have 100g per 10,000 imp gallons for a 1ppm reduction which would (very) roughly be 1/4lb per 10,000 US Gallon for 1ppm in your money, but it would be important to check the instructions as no doubt a store bought chlorine reducer would not be as strong. When using Sodium Thiosulphate it is important not to overshoot, as it can and will strip every residual of Free Chlorine from your pool if overused.

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