Why a difference in FC readings?

[Rick Sass]

I'm using the Taylor 2006 test kit and when I compare my FC readings to those of my pool service company and the local pool store there is quite a difference. The pool store and my pool service company are using the Taylor 2005 kit. All other test readings are quite similiar except the FC test. I'm reading FC at 4.6 while the pool service company and the pool store are reading 3.4. Why the difference in the FC reading?

[chem geek]

This appears to be the same question asked and answered here, except that the readings are a little different (4.6 instead of 4.8 and 3.4 instead of "low 3's").

Richard