High Chlorine Loss but no CC

[houstonguy]

It possible to be losing FC to organics even if testing is showing less than .5 CC. My CYA is 50-60 But I seem to be losing a lot of FC. I added bleach to get it up to 7, yesterday just before sundown. (although I didn't do a drop test to confirm after adding the bleach. I do know it jumped up to 5+ afterwards based on the basic test)

Today at 5:30 pm it was down to 3.5 Does that sound reasonable due to sun alone? Should I be doing an overnight FC loss test even if I don't have an issue with CC?

Thanks!

 

[JasonLion]

Yes, you can have algae or other organics and not have any CC.

With CYA around 50 I would expect you to lose around half of your starting FC level over the course of a sunny day. That fits what you described very well.

 

[houstonguy]

So chlorine loss to sun is typically a percentage rather than an absolute number? If i bump my starting FC up to 8 or 9 I should still expect to lose half that? I was under the impression 2-3 ppm was more the norm....learning new stuff everyday on here.

On a related note, what's the best way to keep the FC where it needs to be if you're away from the pool for a few days? I was using the pucks in a floater before swithcing to BBB so it wasn't an issue.

 

[JasonLion]

If you don't have a SWG, then trichlor tablets in a floater is still a good idea when you are away.