Two water hammer events in a series of "hammer's" are shown in this brief video. Steam at 15 psia from a small boiler precedes to the right in the video atop blue-colored condensate. When the steam reaches the fittings at right in the model, the steam-condensate interface is disturbed causing a further influx of steam which draws up a wave of condensate to plug the glass tube (at left off screen) thereby isolating a steam bubble. As the bubble collapses due to continued rapid condensation, the pressure in the bubble falls into vacuum. With 15 psia pressure then pushing on the upstream side of the plug of condensate, and a partial vacuum resisting on the other side, the slug is accelerated to the right until it comes to an abrupt halt when it collides with the water in the right of the tube. This collision is the waterhammer heard in the video. The four stills captured below in 1/30 sec. increments record the slug moving from the left and colliding at right; or see the Super Slow-Mo version of the video. (The original video was shot by Mark Gitner of Comtec International for Kirsner Consulting Engineering).