Soldering a wet pipe or a pipe that is dripping can be difficult as the water can prevent the solder from sealing the joint correctly. If the pipe is dripping the water can actually be heated into steam which can in itself be dangerous. In this video an old trick from a retired plumber is used where a piece of bread is rolled into a ball and packed into the pipe. Once wet the bread swells up and prevents any water from dripping down and affecting the joint. Once the joint is soldered the bread can be flushed out of the pipe by restoring the water.