FC loss with auto cover

3kidsAndAPool

Well-known member
Apr 17, 2021
121
Kentucky
Pool Size
25500
Surface
Vinyl
Chlorine
Liquid Chlorine
Now that we are swimming, I was wondering what the normal FC loss would be after adding liquid chlorine in the evening and closing the auto cover? I added chlorine to 6.5 ppm two nights ago and then closed the pool. It rained all day yesterday, so I kept it covered and didn’t test any chemicals. This morning I tested and FC was at 4.5 ppm. Is that normal for two days? Also, pool is completely clear. Thanks in advance!
 

3kidsAndAPool

Well-known member
Apr 17, 2021
121
Kentucky
Pool Size
25500
Surface
Vinyl
Chlorine
Liquid Chlorine
Now that we are swimming, I was wondering what the normal FC loss would be after adding liquid chlorine in the evening and closing the auto cover? I added chlorine to 6.5 ppm two nights ago and then closed the pool. It rained all day yesterday, so I kept it covered and didn’t test any chemicals. This morning I tested and FC was at 4.5 ppm. Is that normal for two days? Also, pool is completely clear. Thanks in advance!
 

Kjp300

Gold Supporter
Jul 18, 2018
179
Canfield ohio
Chlorine loss with auto covers can be a bit tricky. What I found with mine is that if I close the cover soon after the swimmers get out I will go through more chlorine because the chlorine is still working on the organics left behind by the swimmers. So the chlorine loss may be 2ppm overnight. And my pool gets a lot of use because I have two granddaughters, aged 7 and 9, who live next door to me and they bring their friends over.

If there has not been swimming and the cover is closed sometimes I will only lose 1ppm over two days. So it depends on usage, how long the cover is open etc. I would think that 2ppm over two days is normal chlorine loss.
 

Kjp300

Gold Supporter
Jul 18, 2018
179
Canfield ohio
Also remember with an auto cover if you test for FC right after you open it many times your CC can be high because the CC is trapped under the cover. If you leave the cover off for an hour or so and test again your CC will return to normal.
 

cowboycasey

Gold Supporter
LifeTime Supporter
TFP Guide
Jul 3, 2013
8,648
Southern OK
Pool Size
15000
Surface
Vinyl
Chlorine
Salt Water Generator
SWG Type
CircuPool SJ-40
Normal... it will depend though.. the cover helps to lower FC use, exactly how much depends on lots of factors... :)
 
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3kidsAndAPool

Well-known member
Apr 17, 2021
121
Kentucky
Pool Size
25500
Surface
Vinyl
Chlorine
Liquid Chlorine
Also remember with an auto cover if you test for FC right after you open it many times your CC can be high because the CC is trapped under the cover. If you leave the cover off for an hour or so and test again your CC will return to normal.
Good info!! Thank you! I’m so paranoid about getting algae that I seem to question everything, lol. This is only our second season, so I’m still learning.
 

Kjp300

Gold Supporter
Jul 18, 2018
179
Canfield ohio
What is your CYA? Mine is 60 and I keep my FC in the 7 range which is higher than the chart recommends. I have been managing my pool that way for three years and never had a problem. Reading these posts I find that too many pool owners try to keep their FC near the minimum and then run into an algae problem
If things go just a little south. If you are worried about algae keep your FC higher. Believe me you and your swimmers will not know and your pool will always be sparkling.
 

3kidsAndAPool

Well-known member
Apr 17, 2021
121
Kentucky
Pool Size
25500
Surface
Vinyl
Chlorine
Liquid Chlorine
What is your CYA? Mine is 60 and I keep my FC in the 7 range which is higher than the chart recommends. I have been managing my pool that way for three years and never had a problem. Reading these posts I find that too many pool owners try to keep their FC near the minimum and then run into an algae problem
If things go just a little south. If you are worried about algae keep your FC higher. Believe me you and your swimmers will not know and your pool will always be sparkling.
My CYA is 30 and I try to keep my FC around 5-6ppm so it has some room to drop during the day. I’m considering increasing it slightly so it doesn’t burn off as fast.
 
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