A snake drain is used if there is hard to reach debris that cannot be cleared immediately. The process starts when the plumber inserts the snake into the clogged drain and manually guides and pushes it into the pipe until the blockage is cleared out. As the metal coil moves down the pipe, it clears out some of the debris and increases water flow. Drain snakes can push holes into debris and allow for a little bit of water flow, but in cases where there are major clogs, the snake drain cannot do much because it does not have the power to clear them out. The same goes with calcification in older pipes or when roots have grown into pipes.