Beyond using a high-powered spurt of water, hydro jetting is a relatively new technology in the plumbing industry that is more environmentally-friendly and less wasteful than other methods of clearing clogged sewer lines and drains.
Basically, a nozzle is fed through the clogged or drained pipe,working from the bottom up. This allows the broken up particles during the hydro jetting process to drain down through gravity. The pressure from the water can self-propel it if need be. There are different types of nozzles that can be used, depending on if we know what material is the source of the clog. When the clog is found, the water is moving at such high force that it acts like a very sharp knife and cuts the clog away. The material, be it food, grease, and more, begins to dissolve, thus ending your clog problem.
Before you begin, however, often your outdoor plumber, such as Dirt Cheap Sewer in Seattle, will use a video inspection kit to see what the clog is. Also, hydro jetting can cause old piping to break, so it's always prudent to investigate the piping before just indiscriminately blasting away at it. Sometimes, a more traditional snake is used first in order to break up heavier material, such as extremely thick tree roots. A video analysis may be done afterwards as well to ensure the entire clog is removed.