SWG percentage very low but FC OK

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K

klanel

Silver Supporter
Jul 11, 2021
540
Athens, GA
I may have the SWG working now or at least it shows it to be working with the app. There are currently no schedules set up in the automation equip and I tend to turn the pump up and down based on usage, time of day and weather related. If we were to have a pool party, pump would probably be on the higher rpm to operate effects and in the nights/evening it would be low rpm and dependent on the weather may turn it up.

Without varying rpms and the current lack of a schedule, how can I best find a comfortable place for settings to maintain the chlorine level? If the pump ran the same speed 24/7 it would be much easier.

Any sugesstions? Thanks
 
K,

The speed of the pump has nothing to do with the amount of chlorine the cell makes as long as the flow switch is closed.

Your pool will use more or less chlorine each day based on swimmer load, sun light, whether etc. You can't set the SWCG so that its output is perfect. You just need to get close.

I have found that the best way for me is to run the cell so that I maintain my target FC level or slightly higher. The only thing I make sure of is that I never get near my FC minimum.

Thanks,

Jim R.
 
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klanel said:
how can I best find a comfortable place for settings to maintain the chlorine level?
Click to expand...
PoolMath will give you a good estimate of different combinations of pump run time and SWG %. Go to "Effect of Adding" ---> "SWG". Start with the SWG adding 4 FC every day, test, and adjust from there.

klanel said:
If the pump ran the same speed 24/7 it would be much easier.
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That would be easier. I operate my pump at 1,000 rpm 24/7, which uses around 75 watts. That equates to ~$6/month in electricity. I like the non-stop skimming, chlorinating, filtering, and circulation. Run your pump for a purpose.
 
Jimrahbe said:
The speed of the pump has nothing to do with the amount of chlorine the cell makes as long as the flow switch is closed.
Click to expand...
I thought I read here that you wanted to oversize your salt cell so you could run a pump at a lower speed and still produce enough chlorine. In my case, I have a 40k gal cell on a 12,500 gal pool. Currently the cell is set at about 50% but I am running my pump on average at 2000 rpm during the day and 1500 at night. If we want a lot of water features going at once, will crank up the pump to 3450.

Are you saying that no matter what speed the pump is running, that the same FC percentage is in the body of water? Or just the same amount produced by the cell with just not as much percentage in the water due to less flow?

I have not, and still don't have a cleaner running but after that is up and going, I may can lower the rpms of the pump during non-water feature times.
pjt said:
PoolMath will give you a good estimate of different combinations of pump run time
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I looked at that section of the app but so far am missing something.
I have the pool volume entered @12500
SWG
24 hr output 40000
Pump run time
SWG 50%
Free chlorine generated 4ppm

Effects - 0 hours pump run time

What am I doing wrong?
 
K,

Just to make sure, here is how a SWCG works.

The cell either makes chlorine or it does not.

To adjust the output of the cell, we just turn the cell on or off for a period of time.

At 50% output the cell will be on about 50% percent of time. Different brands have different on/off times, but at 50% my IC40 is on for 2.5 minutes and off for 2.5 minutes. At 100% it will run continuously.

The 24-hour rating is NOT 40000. Your cell produces X amount of chlorine gas in 24 hours when run at 100%.. Not sure about your specific cell, but it will be in the 22 oz. range. Your manual should say what this amount is.

Pump speed has zero to do with the amount of chlorine your cell makes, no matter what you have read elsewhere. As long at the flow switch is closed the cell can make chlorine.

Thanks,

Jim R.
 
Ok, the cell generates 2.1 #/day. I've had it on 50 % since it was turned on yesterday and the FC was 2.5 ppm this morning. I had been maintaining it with liquid chlorine prior. According to the app, it should raise FC by 10 in 24 hours if set for 50%. I raised the percentage to 56% this evening. The current salt level in the pool is 3260 ppm. Unless I have something mis-configured, it seems to be way off from a FC of 10 estimated to a FC of 2.5 actual. And with the cell rated for 40k and the pool only 12500, seems like the cell isn't producing what it should be. Any thoughts?
 
How long are you running the pump every day?

Perform an OCLT to see if contaminants are consuming FC.
 
pjt said:
How long are you running the pump every day?
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24/7
pjt said:
Perform an OCLT to see if contaminants are consuming FC.
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This morning FC @ 4 ppm with cell @ 50% so it came up some but last night was cooler. Water temp has been 91-93 and this morning mid 80s. I did test once for combined CL which was 0. Have not shut down the cell overnight and checked but will.
 

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klanel said:
Hayward t15
Click to expand...
Please update your signature with that.

PoolMath shows that SWG generating 1.47 lbs./day. Where are you getting 2.1? If your pool volume is accurate, running the pump continuously with the SWG at 50% would increase the FC by 7 every day.

klanel said:
38 kept low because swg wasn’t working and using liquid chlorine
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Round up to the next 10, so let's call your CYA 40. Pass the OCLT before raising the CYA.

klanel said:
Have not shut down the cell overnight and checked but will.
Click to expand...
Let us know if you passed the OCLT or not.
 
FC was just over 4ppm last night and the same this morning with the Swg turned off. I’ve put the swg back at 50%

I did not have the swg model number and chose a Hayward 40000 from the list and that’s where the spec came from. Wondering why one 40k shows one output and another something different when they are both 40k. Either way the t-15 is what’s there.

As for cya, added a couple of pounds over night.
 
klanel said:
FC was just over 4ppm last night and the same this morning with the Swg turned off.
Click to expand...
That's good!

klanel said:
I’ve put the swg back at 50%
Click to expand...
With your pump running constantly, that will increase your FC by 7 every day.

klanel said:
Hayward 40000
Click to expand...
That's not on the list either. The only SWG on the list that produces 2.1 lbs/day is the Pureline Crystal Pure 40,000. In any case, since you have a T-15, your output is 1.47 lbs/day.

klanel said:
Wondering why one 40k shows one output and another something different when they are both 40k.
Click to expand...
Marketing and differences between manufacturers.

klanel said:
As for cya, added a couple of pounds over night.
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Good. What ultimate CYA are you targeting? Remember to increase the FC level as the CYA level rises. Ensure the FC always stays above the target for your CYA: Chlorine / CYA Chart
 
pjt said:
Good. What ultimate CYA are you targeting? Remember to increase the FC level as the CYA level rises. Ensure the FC always stays above the target for your CYA: Chlorine / CYA Chart
Click to expand...
I was intending on targeting about 70 but after looking at the chart, I don't know what benefit there is to raise the CYA if I have to raise the FC as well. Especially since I am able to manage the current FC level at 50% output and haven't had any issues with water quality. Comments?
 
Jimrahbe said:
K,

You will just use up your cell faster, but whatever works for you works for us.

Are you looking at the Saltwater section of this chart? FC/CYA Levels

Jim R.
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Why would it use up the cell faster to have a higher CYA since the FC would have to be higher? Seems like running a higher FC would be more demand on the cell. And from the test I ran last night, the FC stayed almost the same with the cell turned off. OF course, during the day I could see where more CYA would reduce the loss due to UV. So would it be worthwhile to measure FC in the morning and evening to see what loss there is? I'm just learning and feel like being able to have a lower FC would be a good thing but you may know otherwise.
 
K,

The whole point of CYA is to reduce the amount of FC consumed by the sun. Once your FC is increased, it does not take more chlorine to keep it there.

I can't remember if you have an auto-cover or not. If you do, then there is not the same issue you'd have with the sun consuming your FC all day.

Thanks,

Jim R.
 
klanel said:
Why would it use up the cell faster to have a higher CYA since the FC would have to be higher? Seems like running a higher FC would be more demand on the cell. And from the test I ran last night, the FC stayed almost the same with the cell turned off. OF course, during the day I could see where more CYA would reduce the loss due to UV. So would it be worthwhile to measure FC in the morning and evening to see what loss there is? I'm just learning and feel like being able to have a lower FC would be a good thing but you may know otherwise.
Click to expand...
Freeform pool, no autocover but in many ways wish I did!
 
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Jimrahbe said:
Are you looking at the Saltwater section of this chart? FC/CYA Chart

Jim R.
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Yes. Day before yesterday I added a couple of pounds of CYA and FC went from 4.5 to 7. That evening I lowered the SWG from 50 to 45%. I have not checked CYA today but it's probably no greater than 50.
Yesterday evening, FC at 7.7 ppm. This morning at 10 ppm. I have turned off the chlorinator to let the level drop today, will retest later today and then turn it back on.
I am guessing the CYA level has reached a point where the FC loss has been reduced because with the SWG at 50% before, it was never reaching this level of FC. My wife is sensitive to chlorine so I don't want to go to high with the CYA so I can maintain a lower FC.

PS: wouldn't the amount of desired CYA be dependent on how much sunlight a pool gets? We are heavily wooded and get it at this time of year from about 10a to 5p
 

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