At first it looks like a pipe connection going wrong, but this is actually a Victaulic grooved coupling being installed. The pipe will keep flowing until the gasket is fully seated and compressed, which is why the water doesn’t stop immediately. Victaulic connections work by using grooved pipe ends and a rubber gasket inside the coupling. As the bolts tighten, the coupling clamps into the grooves and squeezes the gasket evenly around the joint, gradually closing off the last remaining leak path.