The UVS bulb is burnt out, but I'll set it up anyway just to see. But if I don't have equal pressure on both sides won't it just follow the path of least resistance and go the other way?
There's one PVC ball valve in the box of stuff this came with but given how the tubing was hooked up to the pump I'm not sure how/where that would've been connected. My guess before trying this out would've been that it was on the input, actually.
Anyway, the pump output has a 3/4" ID flexible tube 6" long, then a Y hose barb. Was set up that way when I got it.