Losing Chlorine and SWG possibly not keeping up with demand

[swimmingjax]

Hey everyone,
I started having issues with my FC over the last few days and I'm concerned that I may have a bigger issue.
My FC reading have been pretty consistent for the last several months, usually around 4-5ppm with my SWG set to 30%.
On June 25 my test results were:
FC 5,
CC 0,
PH 7.6,
TA 70,
CH 335,
CYA 70,
Salt 3400,
Temp 83,
CSI -.30
On the 26th I reran CC and PH with the following results:
FC 5,
CC 0,
PH 7.8,
CSI -012
In preparing for the weekend, I tested on Jun 30 and go the following:
FC 1.5,
CC.5,
PH 8,
TA 75,
CH 335,
CYA 80,
Salt 3400,
Temp 90,
CSI .16
I boosted my SWG overnight and got my FC readings up to 4 the next morning with CC of .5.

On July 2, FC dropped again to 2.5, so I increased my SWG to 65% and added bleach to get my FC up, but unfortunatley I'm sure the bleach was no longer effective because 101 oz of bleach only increased my FC to 3.

On July 4, my FC was back down to 1.5 so I added 104 oz of new bleach and got my FC up to 7.5 on the morning of the 4th. I tested again before my party started and FC was at an 8, which I was happy with considering the bathing load.

Last night I tested for OCLT and the results were:
FC 6.5,
CC .5.

This morning at 7:10 FC was at 5.5, CC .5. I raised the SWG to 70%.
At 12:01 FC was holding steady at 5.5 with CC of .5.

My SWG is reporting salt level of 3300 (the other day it was 3200 with no change in actual salt).
The Taylor test returns a salt level of 3400. The ideal level is 3600.

1)Could salt a couple hundred ppm below ideal cause low chlorine output?
2) Considering FC held steady at 5.5 through the morning with the SWG at 70%, does the SWG output seem too high to only maintain that FC?
3) Is there anything else I should check?
4)This afternoon I plan to pull the SWG off and clean it. I did inspect it the other day, and there was only minor scaling on it.

 

[mknauss]

Your salt level is fine.
How much do you run the pump? How much FC do you generate per day at the 70% setting?
You should do a Overnight Chlorine Loss Test
Do not use acid to clean the SWCG unless absolutely necessary.

SWG How It Works - Further Reading

www.troublefreepool.com

 

[proavia]

Please post your test results vertically instead of horizontally. Vertical posted results are easier to review.

FC
CC
pH
TA
CH
CYA
Water temperature
Salt (if you have a SWG)

 

[Mdragger88]

It looks as if you passed the oclt with a 1ppm loss which is within acceptable limits.
Let’s confirm - the swg was off for the duration of the
Overnight Chlorine Loss Test you did - correct?
How does the water look?
Is it Cloudy or any visible algae?
If everything looks great & you feel confident in your oclt results after ensuring there’s no buildup on the cell plates you can do an overnight chlorine gain test (basically the opposite of an oclt with the swg set to 100%) to see how your cell is functioning.
How old is your cell?
Here’s approximately what your cell should be capable of producing in your pool volume in a 24 hour period with optimal performance.

You can play around with the numbers in
PoolMath effects of adding to adjust for your overnight gain test amount of run time.

 

[swimmingjax]

Your salt level is fine.
How much do you run the pump? How much FC do you generate per day at the 70% setting?
You should do a Overnight Chlorine Loss Test
Do not use acid to clean the SWCG unless absolutely necessary.

SWG How It Works - Further Reading

www.troublefreepool.com

Hi, thanks for the reply.
I ran the OCLT last night and result was a loss of 1ppm (6.5 down to 5.5).
On average the pump runs 12 hours a day in the summer, with 2 hours at high speed (3400 rpm) and the rest at 1850 rpm.

I'm not sure how much FC I generate at 70% but the pool math app says that to go from 5.5 to 8 ppm, I need to run my pump at 35% for 12 hours.

Also, i wish I knew about not using Muriatic acid to clean the salt cell. I've probably cleaned it 2-3 times over the last year that way.

Please post your test results vertically instead of horizontally. Vertical posted results are easier to review.

FC
CC
pH
TA
CH
CYA
Water temperature
Salt (if you have a SWG)

Fixed, thanks.

 

[mknauss]

I'm not sure how much FC I generate at 70%

At 12 hours, 4.8 ppm FC.

That is a touch high. Your OCLT technically passed.
If FC is dropping at your current SWCG setting, I would take the FC to SLAM level and see if that cures it.

 

[swimmingjax]

It looks as if you passed the oclt with a 1ppm loss which is within acceptable limits.
Let’s confirm - the swg was off for the duration of the
Overnight Chlorine Loss Test you did - correct?
How does the water look?
Is it Cloudy or any visible algae?
If everything looks great & you feel confident in your oclt results after ensuring there’s no buildup on the cell plates you can do an overnight chlorine gain test (basically the opposite of an oclt with the swg set to 100%) to see how your cell is functioning.
How old is your cell?
Here’s approximately what your cell should be capable of producing in your pool volume in a 24 hour period with optimal performance.
View attachment 510653
You can play around with the numbers in
PoolMath effects of adding to adjust for your overnight gain test amount of run time.

Yes I ran the OCLT with the SWG off. Tested at 9:16pm after the pump shut down, and retested in the morning at 7:10 am before the pump turned on.
The water looks crystal clear with no signs of algae in the water. I did see a few spots of algae in crevacies above the water line on the tile in a place or two but I cleaned that off.
The cell is only 1 year old (pool opened July 4th last year).
I will give the chlorine gain test a try tonight.

 

[proavia]

Pump needs to run at least 30 minutes before testing.

Personally, for the OCLT, I bump my evening FC to 10 and do the nighttime test 30-45 minutes later. I leave the pump running all night and then do the morning test before sunrise.

 

[swimmingjax]

At 12 hours, 4.8 ppm FC.

That is a touch high. Your OCLT technically passed.
If FC is dropping at your current SWCG setting, I would take the FC to SLAM level and see if that cures it.

Thanks, I just figured out how to calculate the chlorine output in the app.
I will test again this evening and if I am still losing chlorine then SLAM may be my next option. My big concern is that I am going to be out of town for week and unable to add chloring if necessary, so hopefully I can at least get this stable enough to get me through the next week.

What can I expect on average for chlorine loss through the day with little to no organics in the water, but full sun and air temp measured around 100 degrees? I think I saw average loss of about 2-3 ppm, but could the extreme heat be causing much higher loss?

 

[mknauss]

My FC loss each day is right at 4 ppm. With full sun, 90F water, and 115+F air temperature. Swimming each day.

 

[swimmingjax]

Pump needs to run at least 30 minutes before testing.

Personally, for the OCLT, I bump my evening FC to 10 and do the nighttime test 30-45 minutes later. I leave the pump running all night and then do the morning test before sunrise.

Ok I'll try that next time I do the OCLT. The pump stopped running at 9 pm, so the test was ran within that 30 minute window.

 

[proavia]

Ok I'll try that next time I do the OCLT. The pump stopped running at 9 pm, so the test was ran within that 30 minute window.

I was more referring to the morning test. You stated you ran the AM test before the pump started.

 

[swimmingjax]

I was more referring to the morning test. You stated you ran the AM test before the pump started.

Gotcha.
I just reread the OCLT instructions and I guess my confusion is that my SWG is tied to my pool circuit, so I figured I needed to shut off the pool pump to shut off the SWG; however, I realized that I can run the pool pump independently of the SWG by letting one of my water features run overnight. That will keep the water circulating without running the SWG.

 

[swimmingjax]

OK so I just retested and
FC - 6
CC -0.

Looks like I gained .5 ppm (I tested 3 times and one of the times I got 6.5 ppm, but I'm going with the 6ppm as official).

I'll test again tonight before the pump stops, but since I gained .5 that leads me to believe that my SWG output was too low for the intense heat over the last week but I will continue to test to validate that.

It is interesting that the pool math app says I only need to run my SWG at 1.25 hours @70% to gain .5 ppm (from 5.5 to 6 ppm), so that isn't anywhere near accurate for my situation.

 

[mknauss]

It is interesting that the pool math app says I only need to run my SWG at 1.25 hours @70% to gain .5 ppm (from 5.5 to 6 ppm), so that isn't anywhere near accurate for my situation.

That is without any loss. During the day, you have FC loss from UV

 

[swimmingjax]

That is without any loss. During the day, you have FC loss from UV

That's what I figured. I'm still too new at this to convert that to a usable loss rate when factoring in UV loss.

 

[swimmingjax]

I ran the FC test again about an hour ago before an afternoon storm rolled through and the FC is still at 6 ( about 3 hours since the last test).
My pool gets full sun from sunrise until around 5 pm when the sun dips behind the trees on the west side of my house, so I get about 4 hours of SWG generation without a heavy UV tax.
With that said, since I am leaving for just over a week should I:
1) Leave SWG at current setting and runtime
2) Increase SWG percentage to 75% or higher while I'm gone
3) Increase FC to 11 PPM right before I leave and keep the SWG at its current level to maintain or reduce FC loss?

I'm planning on testing again tonight (weather dependent). I'm running low on FAS/DPD powder but I should have enough to get me through at least 3 or 4 more tests.

 

[Griswald]

With a CYA of 80, you are flirting with disaster at only 6.0 FC. You don't know if the 6.0 is as low as you get.

 

[swimmingjax]

Last update for the night.
SWG turned off at 9pm but pump still running.
Took reading at 9:15.
FC = 6.5
So slight increase in FC in the 4 hours of shade. I'll test for OCLT tomorrow morning, but I think I may just increase my FC the morning that I leave and let the SWG maintain that as best as it can.
The recommended high FC is 11ppm. Should I increase to that or should I go higher?

 

[swimmingjax]

Well Crud..the OCLT last night failed with a loss of 1.5 ppm.

Looks like I'm slamming when I get home from my trip.

Does that change my target FC before leaving?