# Thread: SWG output compared to bleach

1. ## SWG output compared to bleach

I may install a new pump and SWG next week.

I know that 24oz of 8.25% bleach raises my FC 1 ppm.

how does that compare to pounds of chlorine that the SWG produces?

2. ## Re: SWG output compared to bleach

2 oz of Chlorine gas adds 1.1 FC to 14000 gallons of water.

I'm not really that smart. It's down at the bottom of poolmath under Effects of Adding Chemicals.

Thanks

4. ## Re: SWG output compared to bleach

Originally Posted by WASP
I may install a new pump and SWG next week.

I know that 24oz of 8.25% bleach raises my FC 1 ppm.

how does that compare to pounds of chlorine that the SWG produces?
Part of the confusion around these calculations is caused by the fact that you are (unintentionally, of course) mixing units. The "8.25%" listed on a Clorox bottle is weight percent (wt%) NaOCl (sodium hydroxide). But what you are adding to your pool is a measured volume of the solution (24oz of bleach). So, to figure out how that corresponds to weight of available chlorine (Cl2), one has to do a few calculations and you need to know what the specific gravity (ratio of bleach density to water density) of the bleach used.

So here's the math-

wt% Available chlorine = wt% NaOCl * ((Cl2 molecular weight) / (NaOCl molecular weight)) = 8.25% * (70.906/74.442) = 7.858%

Vol % of Available chlorine (also known as "Trade %") = wt% available chlorine * spec gravity = 7.858 * (~1.11) = 8.722%

So, the bleach you added is -

Vol. of available chlorine = 8.722% * 24oz = 2.1oz chlorine

Weight of available chlorine = Vol. of available chlorine * specific gravity = 2.1 oz * 1.11 = 1.88 oz by weight

So, if you put 1.88oz into PoolMath with your pool volume (14,000 gallons), you'll get 1ppm FC. So, 1.88oz by weight of chlorine gas is equal to 24oz by volume of 8.25% bleach.....or you could just do it like Richard320 did and use PoolMath as all of the equations, calculations, assumptions of specific density, etc, etc, are all built in.

5. ## Re: SWG output compared to bleach

Originally Posted by JoyfulNoise
Part of the confusion around these calculations is caused by the fact that you are (unintentionally, of course) mixing units. The "8.25%" listed on a Clorox bottle is weight percent (wt%) NaOCl (sodium hydroxide). But what you are adding to your pool is a measured volume of the solution (24oz of bleach). So, to figure out how that corresponds to weight of available chlorine (Cl2), one has to do a few calculations and you need to know what the specific gravity (ratio of bleach density to water density) of the bleach used.

So here's the math-

wt% Available chlorine = wt% NaOCl * ((Cl2 molecular weight) / (NaOCl molecular weight)) = 8.25% * (70.906/74.442) = 7.858%

Vol % of Available chlorine (also known as "Trade %") = wt% available chlorine * spec gravity = 7.858 * (~1.11) = 8.722%

So, the bleach you added is -

Vol. of available chlorine = 8.722% * 24oz = 2.1oz chlorine

Weight of available chlorine = Vol. of available chlorine * specific gravity = 2.1 oz * 1.11 = 1.88 oz by weight

So, if you put 1.88oz into PoolMath with your pool volume (14,000 gallons), you'll get 1ppm FC. So, 1.88oz by weight of chlorine gas is equal to 24oz by volume of 8.25% bleach.....or you could just do it like Richard320 did and use PoolMath as all of the equations, calculations, assumptions of specific density, etc, etc, are all built in.
Thank you for the explanation. Though it did make my brain hurt. College chemistry was over 30 years ago. Pool Math is an awesome application.

6. ## Re: SWG output compared to bleach

Matt is a technical Tour de Force, and just as smart as Pool Math.

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