Cool looking PVC choice! You'll be very happy with those valves! What are the two fittings on the return line?
I have read where some people are running a carbon reactor this way and one I’m think on using for water changes might not use either but I figured while I’m there it’s easier to install now
Gotcha! We call it a manifold and I actually run both carbon reactor and GFO reactor(at least used to, don't need it recently) off of one. Yours looks a lot nicer than mine! It's a great way to do that without having to find a space/cash for an additional pump.