drop valve

noun

1. a valve, as for a steam engine, that drops freely to close.

Example Sentences

The drop valve, which opens for a flush, sits underwater at the bottom of the cistern.

From BBC

Most dual-flush toilets use a drop valve system, which was allowed onto the UK market back in 2001 due to a change in regulations.

From BBC

The drop valve is now displacing the slide valve as a better form of excluding or admitting steam.

From Project Gutenberg