I actually haven't measured the flowrate. I think I just assumed that the fluid was going to have to go somewhere. It just seems like those pumps are tough enough that they would pop the tubing if fluid was backing up, I might be wrong though. The one thing I noticed is that you want the fluid to dispense from the top, that way the minerals fall into the main outflow. If you feed it through the bottom, the minerals are to heavy and just sit between the check valve and the outflow (I guess either way the fluid is going to be pushed up eventually, but you have less control).