SWG vs Chlorine not making sense

pjku79

Well-known member
Apr 17, 2015
134
San Antonio
So, I have had my pool installed for a few months now and have been slowly dialing my SWG in over time. Keep in mind my pool is shaded most of the day. It only gets direct sun from about 10am to 4pm (estimate I haven't actually looked). I started out with running my SWG at 70% for about 10 hours based on discussions I had with others on how quickly my FC would drop.

Over the 2 weeks, I had it set all the way down to 30% for 5 hours. I assumed it would be quit low when I got back from my trip. Surprisingly my FC was at 6.5, so on Saturday morning I reduced it by another hour.

With sun both Saturday and Sunday, I measured it last night to find out it had reduced the FC to 5.5.

Am I missing something? Using poolmath and those settings, my SWG is producing 0.5 FC per day. If it only lost 1 FC is two days, that means I am only using 1 FC per day

Started with 6.5
+Produced 1 FC in two days
-Lost 2 FC in two days
=Ended with 5.5

Is this possible? Maybe my percent isn't working right and it is running at 100% (producing 2.5 FC/day). That seems a little more understandable.
 
Last edited:

pjku79

Well-known member
Apr 17, 2015
134
San Antonio
==========================================
Morgan
------------------------------------------
Build Type: Fiberglass
Volume: 11200 gallons
------------------------------------------
Latest Test Result Summary:
FC: 5.5 (18 hours ago)
pH: 8.2 (2 days ago)
TA: 120 (2 days ago)
CH: 275 (2 days ago)
CYA: 50 (one month ago)
SALT: 3800 (12 days ago)
==========================================
 

jimbethesda

Gold Supporter
Jul 2, 2018
277
Austin, TX
I think you meant to say:

Started with 6.5
+Produced 1 FC in two days
-Lost 2 FC in two days
=Ended with 5.5

Which means you only lose 1ppm per day. And your question is why are you only using 1 ppm per day?

Being in San Antonio, that does seem low. Does your pool receive a lot of sun?

You could bring your FC up to 7 and then shut your SWG off for 24 hours. Then you’ll know if you are really only using 1ppm per day, or your SWG is producing more than it should

Either way, this is a good problem to have!
 

pjku79

Well-known member
Apr 17, 2015
134
San Antonio
You are correct, that was a typo on my part. I'll correct it above.

That is actually a good thought. I was going to check it again tonight to see if it dropped at all. If it does, I can increase the time to get it up again and just turn it off to see how much it drops.

Thanks for the suggest.
 

pjku79

Well-known member
Apr 17, 2015
134
San Antonio
Last night it was down to 4 FC. I have some guests coming Wed, so I am going to try to maintain by bumping 30 min. Once they leave, I will try to do a study to see how much it actually drops in one day.
 

Hootz

Bronze Supporter
Feb 5, 2018
122
Rogers, AR
It took me all summer to get my swg dialed in. I have a tendency to over correct so I made myself correct with small adjustments with pump run time or percentage of cell. I found that there was a huge change when I finally got my CYA up to 80. With the CYA at 80 the chlorine consumption lowered considerably...I had to turn down the swg 15 percent or it would over produce.
 
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afbatts

Gold Supporter
May 16, 2018
18
Washinton, LA
I let my SWG run the whole time my pump is running. I just lower the Percentage to make the right amount of chlorine. so i have it set on 15% like Hootz does. Like Hootz once I got my CYA up 70-80 my chlorine consumption was reduced.
 

pjku79

Well-known member
Apr 17, 2015
134
San Antonio
Sorry I got busy with the kids and have just been trying to keep things going.

Now that fall is coming in south texas, I find my self always over chlorinating. I am going to have to start messing with it again. Currently I have the SWG working from 10am to 1pm at 30% and am having to turn it off every few days because my FC gets over 10.

With regards to longevity of the SWG, is it better to have a shorter total time or a lower percent? I figure one has to be better then the other. I am just not sure which it is.
 

Philo

Well-known member
Oct 8, 2015
902
San Diego, Ca.
"With regards to longevity of the SWG, is it better to have a shorter total time or a lower percent? I figure one has to be better then the other. I am just not sure which it is".


They are equal
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
13,271
Northern NJ
The longevity of the cell is more determined by actual 'on time' than anything else. So it's a balance between swcg run time and percentage.
Just to be clear, when you say “on time” you mean chlorine generating time. When cell is powered on and not generating does not reduce cell life.
 

pjku79

Well-known member
Apr 17, 2015
134
San Antonio
Ok so 2 days ago when I measured fc it was at 12.5. I have had my swg off since then and now I have 11. So, now that it's cooled off, I seem to be losing .75 per day.

Before turning it off I was watching my swg a lot more and came to the conclusion that even though I have it scheduled to be on from 10 to 1pm at 30%, it seems to be on all the time at 30%. However the pool pump is only on from 7 to 7, so I guess I'm actually running 12 hours at 30%.

Does that sound more realistic?

Next question is who know anything about Hayward omnilogic?