元もと栓せん

noun

main shutoff valve; stopcock

Refers to the main valve that controls the flow of gas or water into a building. Often used in contexts of turning off the supply for safety or maintenance.

• 地じ震しんの後あとは、まずガスの元もと栓せんを閉しめてください。

  After an earthquake, please first turn off the main gas valve.

• 長ちょう期き間かん家いえを空あけるときは、水すい道どうの元もと栓せんを閉しめておいたほうがいい。

  When you're away from home for a long time, it's better to shut off the main water valve.