Okay, I see. When the switch is turned on, the packager will pass through the packaged water, causing the belt to pass product normally, and when it's turned off, it will cause the smart splitter to become blocked with packaged water and prevent undefined products (anything not packaged water) from continuing onto the belt. So you can block off entire lines when you don't need them. Perhaps you can put an extra smart splitter before the main one, and set it to overflow onto a different line, that way when the device is shut off, it will instead divert product to a different line. You could do this with the space elevator parts to divert them from the elevator to the sink when you don't need them anymore. Or for materials going to a weapons plant. When you've got a nice stockpile, you can divert the materials back to more useful production lines and start it up only when you need to.