DJ: Having used one, I don't think I'd use one again. I love the concept, but in reality, it's not going to create great flow in your tank, so you'll still have to use powerheads and such to create good flow throughout the tank. And in the end, you need to run a bigger pump to create the same flow to your tank, because the SCWD uses like 30% of the flow from the pump to run the internal switching mechanism.
I'm sorry to sound so negative about the SCWD in your thread, Chris, but I just didn't really notice any positive effect on my reef when I used to run one a few years ago. It just caused less flow to actually reach the tank, and every couple months it would clog up with sediment or whatever and then it'd stop switching back and forth until I cleaned it in vinegar for a few hours. Great concept, but the execution left too much to be desired for my liking.
Thanks for the input, but I've used the 3/4" model twice now (both broke... spinner inside snapped off) and really liked them. I am running a Mag 18 on a 58RR, so the 1400gph (after head pressure) is still over kill. The 1" model is rated to 3500gph, so I am thinking the water pressure won't break the spinner off. I already got the unit and it looks well made. We'll see though!?!?! I also don't run any powerheads in the tank which is why I have the larger pump (wanted a clean look).