FC/CC errors in Taylor 2006

[fredricr1]

I just tested my water and the first reading, using the 10ml fill line, required 12 drops, giving me FC = 6. I tested CC and it immediately turned light pink and just barely cleared after 1 drop. I thought this was a tad strange because the pool was fine yesterday (yes, I know this can change quickly). On a whim I rinsed the test tube and re-ran the test using water from the same collection. This time, 14 drops to clear (FC = 7) but NO pink on the CC test. To break the tie, I repeated. 15 drops to clear and a lighter CC pink than from the first test.

Gradually increasing FC readings and variable CC readings on the same water sample (meaning I fill a 12oz bottle of water from the pool and use that sample for all my chemistry tests).

Am I doing something wrong or can this happen? Thoughts?

 

[Flying Tivo]

Someone else on the forum suggest to clean the test tubes with rubbing alcohol to prevent contamination!

 

[Texas Splash]

I wouldn't over-think it too much. You'll beat yourself up over it and go nuts. I'm a bit OCD about my testing, but at a point even I have to say that's it. Since you were using the same water sample for each test, you would assume each test should be very close. The only thing(s) I can think of that might influence those slight changes would be:
- Testing variance from the chemicals themselves
- Contaminants in the testing tube and/or the sample bottle
- Amount of R-0870 powder used
- Slight difference in droplet sizes of R-0871

Even with those items, it's a stretch. Also remember that we consider the CC zero even if it appears to be 0.5. It's so low it's just considered nothing. Overall I suspect you are fine. Today or tomorrow you might run the same tests and find everything matching perfectly.

 

[JoeSelf]

Sample Sizer and Speed Stir really make testing consistent.

 

[scdaren]

I'm getting toward the end of my R-0871 bottle, and I've noticed that sometimes (but not always) the drops seem smaller -- and tests with the new bottle of R-0871 I got result in fewer drops. I just assume my result is 0.5 to 1 less than the drops indicate, and add chlorine to the high end of my target to give myself some cushion.

 

[YippeeSkippy]

I clean the darkening stain out of my chlorine test tube with rubbing alcohol, but I never claimed it was for contaminates. It just really makes the tube sparkle like new again and clear out the stain build up from the test powder. I always rinse well afterwards to remove the alcohol.

Maddie

 

[jblizzle]

There were certainly some threads earlier in the season that kept showing CC values unexpectedly. After they clean the tube, the CC went away.