In chemistry you often heat reactions but don't want any of the liquid to boil away. The solution is to use a condenser on top of your flask-full-of-science. A condenser, like the one pictured here, is simply a double-walled glass tube. You run cold water through the outer portion, which cools any vapor on the inner portion enough that it condenses to liquid again and falls back into the flask.
The slightly warmer water then runs into a sink and down the drain. From there, it tends to become the concern of your municipal waterworks.
Unless, of course, the pipe draining your sink simply runs 40 feet through the wall and fails to connect to anything resembling regular plumbing. In that case, it will fill up the pipe until either the purple laboratory glove shoved into the open end bursts a leak, or until the duct tape holding it in place gives up the fight.
Which, naturally, explains why a lab-mate and I discovered a quarter inch of standing water in one of our rooms just before 5pm on Friday.
