He-pex tubing is a term that refers to Pex that has an oxygen barrier. It looks just like regular Pex that is used for domestic water systems, only it will not allow oxygen to permeate the tube. In a closed loop boiler system, the same water constantly rotates through many bare iron components. This is not a problem because the rust immediately consumes the oxygen and does not continue to eat away at the components. Pex has become very common in water based heating. Regular Pex is often used because it is less expensive and looks identical. However, in the long run it will cost far more because it allows oxygen into the system. This in turn will cause rust to continue to eat at the components and cause premature failure. The pump in the video is less than ten years old and should have lasted twice that long.