draining water from pipes (for winter)
Refers to the seasonal task of draining water from pipes, typically to prevent freezing damage in winter. Often used in household or maintenance contexts.
See also: 水抜き
Before winter comes, please don't forget to drain the water from the pipes in your house.
Compound of 水 (water) and 落とし (dropping, draining), literally 'water dropping'. The exact historical derivation is uncertain, but the term is conventionally associated with the seasonal practice of draining pipes.