TF 100 Test Kit question on results chlorine to FC CC TC

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tfnyla7713

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Apr 28, 2008
19
If I get an FC reading of 3.5 and CC of 0 for a TC of 3.5 and then when I use my small kit, should it read somewhere in the 3.5 area of the scale? I just tested it and the number is closer to 2 than 3.5. Any thoughts? Thank you.

Thomas
 
The small kit (OTO chlorine test) is pretty innaccurate and I would use it to indicate a general range of chlorine.....it can also vary depending on the background lighting.

The drops and powder test (FAS/DPD) is normally on the money and is used when you REALLY want to know exactly how much chlorine is in your pool.
 
CHLORINE

So when I think chlorine I am thinking FC/TC numbers. IF this is correct then with a CYA of 40 the Chemgeek's chart is telling me the FC range is min2.9 to max 4.6. Am I better off at 3.5 or lower being I understand higher chlorine aids staining in pool.

Here are the latest readings I am getting:

FC 3.5
CC 0
TC 3.5
pH 7.2
T/A 100
CH 350
CYA 40

Would appreciate your opinion. Thanks.


Thomas
 
How am I clorinating?

Dave,

Clorox Regular 6% name brand. Using the charge as a guide.

Jason,

I was hoping 3.5 was good - right in the middle. Do you think I should do anything with any of the numbers I've listed?

Thanks.


Thomas
 
Thomas,

Since you're manually chlorinating (which is a good thing) you'll need a range of FC you can live with. You'll lose somewhere around 2ppm daily so I would chlorinate to 5ppm each evening and then test and rechlorinate to 5ppm again the following evening. That should keep your pool in the 3-5ppm range and will be perfect all summer.

You will not be able to maintain a perfectly precise 3.5 unless you chlorinate every couple of hours.
 
Re: CHLORINE

tfnyla7713 said:
Am I better off at 3.5 or lower being I understand higher chlorine aids staining in pool.
Click to expand...
It's not higher Free Chlorine (FC) levels nor even higher FC/CYA ratios that cause staining, but rather adding lots of chlorine for something like shocking the pool that can cause staining via the rise in pH and the presence of metal ions in the water. That is, it is higher pH in the presence of metal ions that causes staining, not high chlorine by itself. If you have water that has iron or copper ions in it (a pool store can test for that if it concerns you), then if you ever need to shock the pool you can minimize the pH rise by lowering the pH first before you shock. As for ongoing use of chlorine, targeting a higher level is not a problem for staining so long as you properly maintain the pH.

As was pointed out by others, what is most important is to always keep the FC at or above the Minimum amount. Going higher is not a problem -- again, if you stay within reasonable pH levels. As a rough point of reference, adding 3 ppm FC to a typical pool would cause the pH to rise from around 7.5 to 7.65 so not that much. It's shocking a pool with lots of chlorine where there is more of an issue regarding pH rise. Adding 10 ppm would have the pH rise from from 7.5 to 8.1 so first lowering the pH to 7.2 would have it rise only to 7.5, for example.

Richard
 

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