Thanks Richard,

I appreciate all of your effort, and I really appreciate the detailed explaination as opposed to the answer only. I am of the curious type and like knowing the logic behind the computations. It gives me a better idea of the workings of the components of my pool chemistry.

I have learned so much in the time I have been a member of this board. This knowledge has resulted in perfectly clear water all summer, with the least amount of time, effort and $$$.