Is CC= 0.5 ok?

BIC

Well-known member
Jul 7, 2007
108
#1
I use a SWG and I have a AG pool 24 feet. For the last 3 weeks it has been raining a lot (I thought I should mention that).

FC = 5
CC = 0.5
CYA = 60-65

I just want to know if it is normal to have a CC = 0.5. After I tested the FC with TF-Kit, my water had a very little tint of Pink (very little), by adding one drop the water turned back totally clear (1 drop x 0.5 = 0.5 of CC).

Is the CC = 0.5 normal or should it be 0 all the time?

BIC
 

JasonLion

TFP Expert
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LifeTime Supporter
May 7, 2007
37,879
Silver Spring, MD
#2
CC of 0.5 is fine. The rain has probably brought some debris, which could cause the CC reading.

[[Note: With the FAS-DPD test, one drop to clear CC is fine, so if you are testing so that one drop is 0.2, then 0.2 is fine but 0.4 is a problem.]]
 

BIC

Well-known member
Jul 7, 2007
108
#3
JasonLion said:
CC of 0.5 is fine. The rain has probably brought some debris, which could cause the CC reading.

[[Note: With the FAS-DPD test, one drop to clear CC is fine, so if you are testing so that one drop is 0.2, then 0.2 is fine but 0.4 is a problem.]]
With the TF-Kit: one drop is 0.5

I don't get the idea. Is it the number of drops that counts or the value at the end? So if 0.5 is ok, that means that 0.2 x 2 drops = 0.4 cc should be fine too? But your are kind of saying it would not be ok?
 

JasonLion

TFP Expert
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LifeTime Supporter
May 7, 2007
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Silver Spring, MD
#4
There are two ways to do the FAS-DPD test. The instructions with the TF-100 are for measuring by 0.5 per drop. But the same reagents can be used with different instructions to test for 0.2 per drop.

The simple rule is that one drop to clear CC with a FAS-DPD test is just fine.

The way things really work is more involved. It all hinges on how the test works. One drop to clear CC means that the actual CC level is above zero but not more than 0.2 or 0.5 (depending on how you do the test). In practice the CC level is almost always much closer to zero than it is to 0.2 or 0.5. We still call the level 0.2 or 0.5, but if you had a more precise test the true level would almost always be much lower.

CC starts to cause problems when the true level is around 0.4. Using the test at 0.2 per drop it is easy to tell if you are below 0.4. Using the test at 0.5 per drop, if the test reads one drop you can't really be sure you are below 0.4, but the odds are very much in your favor that the level is actually below 0.4. In an outdoor pool, the odds that everything is fine are so good, that we don't bother to tell you to do the test over again with the other instructions to get a more precise level, it would just be a waste of time.