Jim Goedert, EWB-NE Professional; Dwight Hanson EWB-NE-P President ; and Ben Pavlik EWB-NE Student install the modified first flush piping. on St. John’s Clinic. The first flush system is a vertical pipe into which the first rainfall from the roof washes at the beginning of a rainfall event. The water from the first flush contains dirt and debris that accumulates on the roof during the dry period. Once the vertical pipe of the first flush system fills; cleaner water flows over it and into the water tanks. The first flush system helps prevent the tanks from filling with dirt and keeps the water in the tank cleaner.