In such drip irrigation pipes, the outlet may be in the form of a flap that is formed in the wall of the pipe. German Patent No. 102004059721 describes an irrigation hose that has several longitudinal flap type discharge openings formed by sectional grooves in the hose wall and flow limiters that are arranged at the inside portion of the hose within the range of the discharge openings.
U.S. Patent Application No. 2006186228, the disclosure of which is incorporated herein by reference, describes a dripper bonded to a pipe wall that in an embodiment has two slits that are made into the pipe to form flap type outlet opening each in fluid communication with an outlet area of the dripper.