Richard, no offense taken in any of the responses here. What's interesting is that scientific calculations "should" prove to be consistent with lab conditions, and I'm sure it does. However, real world applications show differently, mainly due to (IMHO) external parameters that are too diverse to pinpoint.

My unscientific mind says that what I see in real life, is what I can report on. Just like Ben's best guess charts are based on his many years of actual experience and research and have proven highly effective. The longevity and membership here, proves that point. Who would have ever thought to grab the gallon of bleach and box of 20 mule team from the laundry room to take care of a pool?!
Ben's wife must have absolutely killed him the first time she saw him sneaking off with the bottle of Chlorox!

You chemistry GEEKS, sorry Chemgeek for borrowing on your name, absolutely are amazing with your knowledge. I have a hard enough time converting Celsius to Fahrenheit! I cheat and just double ( I THINK it's suppose to be times 9/5, rather than times 2) the Celsius and add 32.
I have to admit though, I am learning quite a bit from this string.

Thanks y'all