Each and every beer we make has to be racked at least once during its lifespan. While professional brewers typically rely on pumps to move beer between stainless steel vessels, homebrewers usually employ a siphon.
We all intuitively understand the principle of a siphon. You position a container of beer or wort above the carboy or bucket into which you’d like to transfer. One end of a length of flexible tubing goes in the upper container, and the other goes in the lower container. Once the liquid starts moving, the siphon maintains itself until all the liquid is transferred. But starting the siphon in the first place can be awkward.
You could suck on the free end of the tubing to get the liquid flowing, but this isn’t very sanitary. If you start a siphon this way, you risk contaminating the batch with all kinds of hungry microbes that live in your mouth.