A backflow preventer for water distribution installations includes a body having an inlet conduit arranged along an inlet axis, an outlet conduit arranged along an outlet axis, and a discharge conduit arranged along a discharge axis of the body. The backflow preventer is provided with check valves that prevent a backflow of fluid from the outlet to the inlet in the event of low pressure upstream of the backflow preventer and/or high pressure downstream of the backflow preventer. The backflow preventer further includes a discharge valve arranged along the discharge axis of the body of the backflow preventer for discharging fluid in the low and/or high pressure conditions. A discharge pipe is connected to the discharge valve to discharge the fluid outside the backflow preventer along an end discharging axis of the fluid outside the backflow preventer. Coupling elements are provided to adapt the backflow preventer to various applications for varying the angular position of the discharge pipe with respect to the body of the backflow preventer.