the math of SWG chlorine production

uosuof

Member
Sep 8, 2020
15
Toronto, Ontario, Canada
Hi there - first poster here. Incredible forum - thx so much to the brains out there contributing! Have been reading up voraciously to educated myself as I am in the process of having my first pool built - which is still a few months away from completion.

I'm currently finalizing design and specs w/PB and need to understand chlorine generation capacity of SWG. The one PB recommends is Jandy AcquaPure 1400, which is rated for a 40k gallon pool and supposedly produces 1.25lbs/day of chlorine.

Now, the pool I'll get will likely be around 17,500 gallons. If I get the math right, this equals ~148,000 lbs of water. If, as I understand, 1 ppm of chlorine equals 1 lbs of chlorine in 1,000,000 lbs of water, this would seem to suggest that:
(i) in my case, 1 ppm of chlorine equals ~0.148 lbs (or ~2.4 oz) of chlorine;
(ii) if I want to target, say, 6 ppm of chlorine in my water starting from zero, I would need to add 0.888 lbs (or ~14.2 oz) of chlorine in my pool; and
(iii) once I reach my 6 ppm target, and assuming that I have no algae and my only FC loss is due to UV exposure and that I am losing, say, 2 ppm daily based on that sun exposure, THEN it would seem that my SWG would need to replace/produce only 2 ppm daily which in my case is ~0.3 lbs of chlorine.

(btw I know the numbers are fictitious, but pls play along - I just want to understand if I am getting the math right here).

When the SWG specs say it is rated for 1.25 lbs of chlorine production per 24hrs, what exactly does that mean? Is it assuming that the SWG is set to run at 100% capacity 24hrs/day? If so, would it logically follow that I would get that SWG to produce my needed 0.3 lbs of chlorine by:
(a) running it 24hrs/day at 25% capacity (since 25% of 1.25 lbs is ~0.3 lbs); or
(b) running it 6hrs/day at 100% capacity (since at 100% capacity it produces 1.25 lbs or 0.052 lbs per hour, and 0.052 x 6hrs = 0.3 lbs of chlorine).

To me, (a) or (b) should be equal in terms of chlorination and both meet my requirements in this example. Is this correct? And if so, is there a difference between (a) and (b) in terms of life shelf of the SWG (running it constantly at lower power vs. shorter runs at full power)?

Thx so much for your help validating my thoughts
 

Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
Welcome to TFP! :wave: Congrats on the new pool adventure. There are some here who will be happy to break-down the SWG math numbers for you, but I prefer to keep it relatively simple. We recommend a SWG that is rated for at least 2Xs the size of your pool, which you have already done. Remember that SWGs produces chlorine "gas" versus liquid chlorine, so the pounds comparisons are not similar. It's best to use the TFP PoolMath APP to analyze FC production> The APP has a feature fo r "Effects of Chemicals" and can show you the anticipated amount of chlorine produced, either at it's max rating (24 hrs @ 100%), or broken down by any other factor you would like. But if you get a 40K-rated SWG for a 17.k gallon pool, you should do just fine.
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
22,295
Northern NJ
Pool Size
35000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-60
Welcome to TFP.

The PoolMath Effects of Adding feature can do all the SWG calculations for you. Or you can see this SWG Runtime Spreadsheet.

When the SWG specs say it is rated for 1.25 lbs of chlorine production per 24hrs, what exactly does that mean? Is it assuming that the SWG is set to run at 100% capacity 24hrs/day?

Correct. Stated chlorine output assumes runningb the cell at 100% 24/7.


If so, would it logically follow that I would get that SWG to produce my needed 0.3 lbs of chlorine by:
(a) running it 24hrs/day at 25% capacity (since 25% of 1.25 lbs is ~0.3 lbs); or
(b) running it 6hrs/day at 100% capacity (since at 100% capacity it produces 1.25 lbs or 0.052 lbs per hour, and 0.052 x 6hrs = 0.3 lbs of chlorine).

To me, (a) or (b) should be equal in terms of chlorination and both meet my requirements in this example. Is this correct? And if so, is there a difference between (a) and (b) in terms of life shelf of the SWG (running it constantly at lower power vs. shorter runs at full power)?

No difference in cell life. Cell life is determined by the amount of chlorine it has created. Any combination of % and runtime to give the same chlorine output depletes the cell life the same amount.
 

uosuof

Member
Sep 8, 2020
15
Toronto, Ontario, Canada
Welcome to TFP.

The PoolMath Effects of Adding feature can do all the SWG calculations for you. Or you can see this SWG Runtime Spreadsheet.



Correct. Stated chlorine output assumes runningb the cell at 100% 24/7.




No difference in cell life. Cell life is determined by the amount of chlorine it has created. Any combination of % and runtime to give the same chlorine output depletes the cell life the same amount.

Thx so much for addressing my questions quickly. Glad I'm starting to get the hang of this. I will play around with pool math and the SWG spreadsheet you linked till i figure out the right ratios.
 

uosuof

Member
Sep 8, 2020
15
Toronto, Ontario, Canada
Remember that SWGs produces chlorine "gas" versus liquid chlorine, so the pounds comparisons are not similar.

I didnt think about this at all. I will need to research this a bit to figure it out I guess. Sure will use the pool math app, but I like to understand the logic behind the app rather than just blindly using its output.. thx for your suggestion
 
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