Liquid pump

A liquid pump comprising:

• a container body confining a receiving space and having an upper portion, a lower portion, a vent hole formed in said upper portion, a cap mounted removably on said upper portion for closing said vent hole, a liquid inlet formed in said upper portion, a guide tube connected to said liquid inlet, a liquid outlet formed in said lower portion, and a plug mounted removably on said lower portion for closing said liquid outlet;
• a vacuuming device mounted on said container body and operable so as to reduce air pressure within said container body;
• and
• a liquid-discharging device including a connecting rod connected to said plug and movable between a closing position, where said plug closes said liquid outlet, and an opening position, where said plug is removed from said liquid outlet, said liquid-discharging device further including a biasing unit connected to said connecting rod for biasing said connecting rod to the closing position.