Emitter
An emitter is also called a dripper and is used to transfer water from a pipe or tube to the area that is to be irrigated. Typical emitter flow rates are from 0.16 to 4.0 U.S. gallons per hour (0.6 to 16 L/h). In many emitters, flow will vary with pressure, while some emitters are pressure compensating.
These emitters employ silicone diaphragms or other means to allow them to maintain a near-constant flow over a range of pressures, for example from 10 to 50 psi (70 to 350 kPa).
Read more about this topic: Drip Irrigation