The Delta 1 Hose Bibb Vacuum Breaker is an anti-siphon that prevents contaminated water from flowing back into the clean water supply.This vacuum breaker can be used in darkroomsAlmost all the U.S. plumbing codes and EPA compliance regulations state that you should fit this water control in the plumbing systemOn both ends, this darkroom sink accessory has screw on spout and garden hose thread fittings