FC/CC question

[poolcarma]

Hi all,

I am a bit confused about my chlorine testing. Here are my overnight numbers:

8:30 pm

FC-20.5
CC- .5
TC-21.0

5:45 am

FC-13.5
CC- .5
TC-14.0

It's obvious that I still have algae ( -7 FC overnight ). What I don't understand is why my CC's are so low. I have the pool sweep running constantly with the filter. Can it be cleaning it up that fast?


Readings from 8/24 before the shock process started:
FC- .5
CC- .5 ( This is when I realized my SWG is not working properly!)
TC- 1
pH-7.5
TA-130
CH-410
CYA-60

Yep! My water has issues!

poolcarma (Just keep scrubbing, just keep scrubbing.)

 

[duraleigh]

What I don't understand is why my CC's are so low.

Combined Chloramines are a good indicator that you do have algae but they are not neccessarily an indicator that you don't have algae. A little confusing, huh? I'm good at that.

A CC test result of 1.0 or greater is almost a dead giveaway your pool needs to be shocked. Others here can explain the chemistry more clearly than I.

However, algae can (and does in your case) easily exist without the presence of CC's. Again, perhaps we'll get some help explaining the chemistry

 

[JasonLion]

When fighting algae, CC is constantly being both created and broken down. When chlorine first contacts the algae it forms CC. Then additional chlorine breaks down the CC. CC only shows up on the test when it is being created more quickly than it is being broken down.

As long as you are maintaining reasonably high FC levels, CC will typically be broken down more quickly than it is being created. CC tends to accumulate at relatively low FC levels, when there is enough chlorine to kill algae, but not enough to break down the resulting CC.

 

[poolcarma]

Thanks!

I'm glad something about my water makes some sense!


Since we're talking chlorine.........

It's still very hot (over 100 degrees)and sunny where I am, and I'm wondering about chlorine loss during the day. Since I'm trying to maintain shock levels, should I go out every hour or so and check the chlorine? Should I shock at a higher level?

Thanks for your help!
poolcarma

 

[JasonLion]

I suggest testing and adding chlorine every hour until the FC level starts to mostly hold. Once FC is remaining at 80% or higher of it's original value after an hour you can switch to three times a day.

 

[poolcarma]

Thanks, I'll keep keepin' on!

poolcarma