The flowing water erodes manure lying in its path and the loosened particles are suspended in the flowing stream. The erosion type flush system developed as people wished to build barns with reduced slopes or wanted to avoid having a large tank situated at the head of the alley. But erosion type flushing requires substantially larger quantities of water. As a result, water is often recycled from manure storage for erosion flush systems. A smooth transition as the water changes direction upon entering and being directed down the alley maximizes the energy converted to a velocity head, the energy used to set the water in motion.
Water loses velocity as it moves down the alley due to friction and other forces.
In principle, flushing is accomplished as manure solids are floated away by the moving water stream. Tip tanks, elevated a few feet above the alley, that empty backwards directing water onto a curved surface for a smooth transition onto the alley surface most efficiently convert elevation head to velocity head. About 75 to 100 gallons of water per cow per day will be needed. Thus, the motivation to recycle water is obvious. Again, the amount of water to be used depends upon how the water is released.