FC loss is stumpimg me...

[johnd13]

Ok, it's been really hot and humid here... 95 to 100 degrees and high heat index the past week. My pool is not screened and gets about 10 hours of full sun a day right now. My pool temp was 90 yesterday afternoon, like bathwater.....

I have seen a loss of 7 in my FC during the day (i turned off my SWG during the day to see what the loss actually was). I do the overnight loss test and no loss and no CC. My numbers:

FC 9.0
CC 0.0
TC 9.0
TA 90 (been getting it down)
pH 7.2 (again, adding MA and aerating to get TA down)
CYA 50
CH 300

After confirming no overnight loss, I just added 5 lbs of stabilizer to raise the CYA.

I am running my SWG at almost 60% just to keep my FC in a safe range.

Can the sun knock my FC down by 7 during a hot summer day with my CYA at 50?

 

[JohnT]

Chlorine loss due to the sun is proportional to chlorine level. Do you lose all the chlorine when running at normal levels (3-4ppm)?

The CYA test is pretty subjective, so the accuracy isn't great

 

[JasonLion]

High water temperatures and extra sunlight in the early/mid summer will use up way more chlorine each day than colder water temperatures and spring/fall levels of sunlight.

Also, with a SWG you want CYA around 70 to 80, which will also help reduce chlorine loss significantly.

 

[johnd13]

Chlorine loss due to the sun is proportional to chlorine level. Do you lose all the chlorine when running at normal levels (3-4ppm)?

I try and keep my chlorine level at 5. I am a little apprehensive about starting off the day at 3-4 and seeing if I lose it all...

The CYA test is pretty subjective, so the accuracy isn't great

Believe me, if I could find a way to have my CYA read for me I would. I read it three times and was right around 50 each time....

 

[johnd13]

High water temperatures and extra sunlight in the early/mid summer will use up way more chlorine each day than colder water temperatures and spring/fall levels of sunlight.

Also, with a SWG you want CYA around 70 to 80, which will also help reduce chlorine loss significantly.

CYA on its way up to 75 now according the the Pool Calculator after I added the stabilizer. I delayed raising the CYA until I confirmed no overnight loss to cut back on the chlorine needed in case I had to shock it. I'll keep an eye on it as the CYA rises and see if my daily FC loss goes down

 

[ajones02]

johnd13, i seem to have had a similar issue. for some reason i had some CYA disappear and still do not know why. i added some stabilizer back last week to get it back up to 80. i currently have my SWG set at 75% just to keep up with the chlorine loss on a daily basis and to keep the chlorine at the 6 ppm target. same here with full sun all day long. zero shade.

 

[johnd13]

I got my CYA up to 80 and the SWG is now at 50% and my FC is holding at 6.....