Main pipe and Trunk line

Trunk line and main pipe are semantically related in road topic. In some cases you can use "Trunk line" instead a noun "Main pipe", when it comes to topics like main line, mainline.

Trunk line noun - A telephone line connecting two exchanges directly.

Main pipe and trunk line are semantically related in road topic. You can use "Main pipe" instead a noun phrase "Trunk line", if it concerns topics such as main line, mainline.