Transmission and distribution piping can constitute a significant cost component in a geothermal system. For district heating systems, the cost associated with the distribution network is frequently 40 - 60% . of the overall capital cost of the project. For this reason, it is important to select the least cost material which is suitable for the application. The information contained in this report is intended to provide a background for the selection of piping for direct buried service in low temperature ( < 250°F) geothermal district heating systems