How is this even possible???

Sorry to keep bothering everyone, but I am about to go crazy. As mentioned in my other posts, I am shocking my pool due to one reason: an overnight FCL of 1.5. Everything else is fine. But as I mentioned also, when I started shocking, I got a 4.5 drop in FC overnight. I thought that was weird enough, but today I have been pampering the pool trying to keep it at or above shock level, and now things are defying logic. I added bleach this morning and brought FC up to 22 (Shock level is 20 for my CYA). Two hours later, I was at 19. Okay, extreme sunlight loss, I assumed. I bumped it back up to 23 this time. ONE hour later I was at 19 again! Weird enough? Not yet: I bumped it back to 23, let it mix for about 30 minutes, and then decided to bump it higher so that I didn't fall below 20 again. I added half a gallon more bleach, waited 40 minutes; and I was at 22! Adding bleach brought it down! I thought maybe my titrating reagent was bad. I had another bottle, luckily, and retested; same result. I've tried getting water samples from different areas; same result. What the heck is going on!?
 
You should keep all your posts under one thread for continuity and so others can read your whole story.

That said, what you report is absolutely normal. Two things consume chlorine......organics in your pool and sunlight. Some combination of those is consuming your chlorine. Why does that seem unusual to you?
 
Sorry for the multiple posts. I will keep them under one thread next time. It seems unusual because under normal FC levels I was losing 3ppm chlorine all day long, and 1.5 overnight, and then suddenly when I start shocking I am losing 3-5 ppm in a matter of 1 hour and 4 ppm overnight. Why would the loss increase so wildly? And how could adding half a gallon of bleach result in a 1ppm LOSS in 40 minutes?

Is it perhaps that at shock levels the chlorine is getting used at a MUCH more rapid pace?
 
I think part of what you see seeing is that with as given CYA level, you will lose a % of your FC to the sun. Since you are at higher FC values, that % is a higher FC ppm. Losing 3 out of 20 is a lot lower % than out of 6.

This may not be exactly correct, but the basic idea I think.

Posted from my Droid with Tapatalk ... sorry if my response is short ;)
 
Thread Status
Hello , This thread has been inactive for over 60 days. New postings here are unlikely to be seen or responded to by other members. For better visibility, consider Starting A New Thread.