Blckbrd, you don't want the juniors, those ones water through the cone, not the line.
The valves have to be filled with water and then soaked overnight to activate them, then pushed into an overwatered medium. Then they will start working. If they dry out they have to be pulled and reactivated again. I'm planning on adding some drip-clean to my reservoirs to help keep the tiny 3mm tubing clean and free-flowing too.
The only other system I know of that is demand-based is a wick system, which I don't think would be practical for large grows. Not that the Blumats are entirely practical either, but I've designed my reservoirs around them.
have a look here.......
http://www.icmag.com/ic/showthread.php?t=111046