Microirrigation Submain Unit with Pressure Reducing Pipes

A pressure reducing pipe (PRP), used at the inlet of a lateral in microirrigation systems to improve water application uniformity, is developed. It is composed of an internal spiral and a sleeve pipe and is made of molded polyethylene plastic. It functions to dissipate a pressure head that exceeds the required pressure head of a lateral inlet by directing water flow through the spiral grooved path and creating a certain head loss. An improved design method for submain units using the pressure reducing pipes is based on the hydraulics of the submain unit and the characteristics of the head loss in the PRP. The effects of the PRP on water application uniformity in a submain unit are analyzed by computer simulation. The submain unit with the PRP has higher uniformity than that of the commonly used method. After choosing the PRP, the permissible range of pressure variation in a submain will not need to be considered for the submain length in a layout. ©2002 American Society of Civil Engineers