Free Chlorine is negative

[Richard320]

Out of boredom and my childlike obsession with my new toy (TF100) I decided to test my tap water.

pH 7.6
TC .2
CC 1.2
CH 400
TA 170

So obviously they use chloramines in my local water supply. That would give me a -1.0 Free Chlorine. I searched using "chloramine" and only got one hit, which was no help at all.

Oh well, nothing I can do about what comes out the tap.

 

[Bama Rambler]

Since you can't really have negative chlorine and given the fact that TC is the sum of CC and FC I suspect that maybe you have a testing error or at least a reading error.

Oh, and don't feel to childlike, I've tested my tap water more than once!

 

[Butterfly]

....Oh, and don't feel to childlike, I've tested my tap water more than once!

Me, too, and I do not drink it

 

[JasonLion]

If you are testing with the TF100, the FAS-DPD chlorine test they include (the one that uses R-0870 and R-0871) measures FC and CC. From those two numbers you can calculate TC. I suspect that you were actually measuring an FC level of 0.2, and mistakenly called it TC.

By the by, seeing noticeable CC levels in tap water is very common and doesn't mean the same thing it does in a swimming pool. Many public water companies are switching to disinfecting with chloramine, which will test as CC. When you fill your pool with tap water, the chloramine goes away after a day or so and doesn't cause any problems.

 

[PoolGuyNJ]

Knowing what your fill water is helps you know what you'll need when you add water.

Scott

 

[Richard320]

If you are testing with the TF100, the FAS-DPD chlorine test they include (the one that uses R-0870 and R-0871) measures FC and CC. From those two numbers you can calculate TC. I suspect that you were actually measuring an FC level of 0.2, and mistakenly called it TC.

You are correct. I was using the powder. Guess I'm just used to the drop method.