3N-COUNT [usually plural](室内煤气、自来水或污水的)总管道,主管道 The mains are the pipes which supply gas or water to buildings, or which take sewage away from them. (室内煤气、自来水或污水的)总管道,主管道
...the water supply from the mains.
总管道的自来水供应
The capital has been without mains water since Wednesday night.
从周三晚上开始,首都就停水了。
4N-PLURAL 电力线;电源The mains are the wires which supply electricity to buildings, or the place where the wires end inside the building. 电力线;电源 [mainly British]