Mixing copper types?

Yes, it's fine to mix them, especially if you're going with thicker, or K in place of L. The wall is thicker, so you might experience a minimal flow difference, but I can't imagine that would be significant. Going the other direction, L in place of K, unless you're working under extreme pressures where you need the additional wall thickness, I can't imagine it would make any difference. The external diameter remains constant on all of them so fittings fit.

Harold

Thanks for the info Harold!! Josh