元栓

1. Origins, structure, and basic meaning

• Structure: 元栓 is read as もとせん and is a noun for the main shutoff valve controlling an entire gas or water supply.
• Basic usage: Checking the location of the main valve appears in 元栓の位置を確認する, while describing a red mark on the main valve appears in 元栓に赤い印がある.

2. Common pitfalls and similar expressions

• Difference from 蛇口
  • 元栓 controls the whole supply rather than a faucet at one point.