 Among other things, the summer camp students have been learning to design games, model houses, and how to filter so-called gray water from showers, washing machines, and kitchen and bathroom sinks. Jim Cressula, CBS News. Setting a 30-minute timer on your phone after eating before you hop into the pool? Doctors say you can knock that off, as in most cases, there's no need to wait unless you're planning to swim laps or exercise in the water.