Quote Originally Posted by autobot View Post
Looking at those pictures raises a questions in my mind. What is to stop the fluid from simply flowing from one barb to the other? There is no seal in the middle section between the channels. There even appears to be a small gap between the acrylic and copper in those pictures.
Good observation, but it's really no different than many other full coverage blocks unless they have a seal that wraps around internally as well. Danger Den is the only one I've seen do that, so you'll get some internal leaking on the others as well.

But I wouldn't worry about it, internal leaks usually don't amount to much unless the block is fairly restrictive if sealed up completely. It usually means less pressure drop which means your pump produces more flow which mitigates the issue pretty well. I've done a couple of experiments around sealing different blocks up completely and most don't net any measureable gains.