There are indeed baffles/chambers, but they have holes between the walls. Here's an old pic. from Brian Brave. http://i301.photobucket.com/albums/n.../SurgeTank.jpg
I prefer a separate vented (zero pressure) tank for easy filling/monitoring of the IC system. My little spit tank allows me to actually see the pump working/flowing. I copied this Mod from Tunaglove.