The phrase "water drain" refers to a hole or pipe that lets water flow out of a particular location, such as a sink, bathtub, or street. It helps prevent water from accumulating and causing problems. Full definition
The principle is simple: cold water draining into a tank beneath the platforms is pumped through the heat exchange unit to cool air. (newscientist.com)
If the amount of water entering the tub from the faucet is the same as the amount of water draining out of the tub, the water level won't change. (skepticalscience.com)
After a few minutes, remove the cabbage and let the excess water drain away. (azgrabaplate.com)