I have just finished with my PEX supply lines to all the bathrooms and kitchen, and now I am ready to install the recirculation line.

I have a 2 story house with my HWH in the basement, a powder room and kitchen on the first floor and bathrooms upstairs. They each have a separate pex line, as shown approx in the are in the attached diagram. The blue arrows are my guesses as to where the hot water would come from if I use any of those fixtures (when just the pump is running, then those arrows are obviously not accurate).

Name:  recirc-plan.jpg
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My confusion now is that if I install the recirc line as drawn, then it seems like, for example, the kitchen sink would pull in water from any of the tubes? Is that a problem? Is 1/2" the right size? As an alternative, would it be better to have each distant fixture have its own recirculation line, then converge them all at the pump - each with a separate check valve?