# Thread: Check My Math

1. ## Check My Math

I calculated the equivalent amount of 12.5% bleach (with specific gravity of 1.2) to the output of my SWG to determine what my daily use would be if I were switch to manual dosing. I run my pump for 12 hours per day (at a low RPM) and currently have the SWG output set at 30%. My SWG produces 0.567KG of chlorine gas at 100% output per 24 hour period.

The conversion is as follows:

0.567KG/12.5%=4.536KG

4.536KG/1.2=3.78 Liters of 12.5% bleach per day at 100% output

3.78L x 12/24 x 0.3 = 0.567L (or 19.2 OZ) per day at my current pump run time and SWG output

Questions:

1. Is my calculation method correct?

2. Is 19.2OZ of 12.5% bleach per day a typical amount for an 18K gallon pool with a CYA of 70-75? Using Poolmath, that's only a 1PPM increase per day.

Thanks for the help.

2. ## Re: Check My Math

.567 Kg is 567g and in your 18000 gallon (68137L )pool, poolmath says it would add 8.3 FC

8.3 ppm cut in half for 12 hours pump time and then multiplied by .3 for SWG% yields 1.3 FC loss per day.

To raise your pool 1.3 ppm FC will take .7L or 24 oz of 12.5%

EXCEPT your pool will now be a bleach pool so the recommended minimum goes up which means losses to the sun also go up so you'll probably need more

I use about a quart of 12.5% a day in my 16000 gallon pool. So you'll likely use slightly more than that.

3. ## Re: Check My Math

Richard,

Thanks for double checking me. My math using the specific gravity of the liquid is probably overkill but I'm an engineer. I can't help it.

Been using a SWG for several years now so I forgot that the recommended minimum would go up if I start dosing manually. For budgeting my 12.5% bleach usage, I will probably use a daily 1.8 PPM FC loss to estimate my bleach usage and see how it goes. I am also considering a Stenner pump and need a decent estimate to determine tank size.

Thanks again.

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