"But those sources you list describe several types of check valves, all of which have moving parts." Most all check valves use moving parts; the Tesla Valve is

"But those sources you list describe several types of check valves, all of which have moving parts." Most all check valves use moving parts; the Tesla Valve is novel because it does not. I added the sources for those that might want to satisfy their curiosity when thinking, "I wonder what type of device a Tesla Valve is?" Although the Tesla Valve does not use moving parts, that does not mean that it is not classified as a check valve. Tesla's descriptions from his patent [1] describe the valve as only permitting flow through it in one direction, which is the essential operation of a check valve: "[...] a series of recesses or pockets with surfaces that reverse a fluid tending to flow in one direction therein and thereby check or prevent flow of the fluid in that direction." (Page 5, Item 3) "[...] and thereby check their progress when impelled in the opposite sense." (Page 5, Item 5) "[...] reverse such fluid impulses when impelled in the opposite direction and check their flow." (Page 5, Item 6) [1] http://www.google.com/patents?id=Lt1PAAAAEBAJ http://www.google.com/patents?id=Lt1PAAAAEBAJ