Hi there!

I am adding a vanity with two sinks into a bathroom that has pluming for one sink. The pluming is right in the middle of the vanity. I want to use the existing pluming for both sinks. What I have read is that the spacing of the sinks should be no more than 30 inches apart. What I am curious of is that 30 inch on center no matter where the pluming is? Or is it no more than 30 inches from where the p-trap is for each sink?

P.S. everywhere I look people reference "check with local building codes". I live in California, is there a website that lists building codes for us?