In older homes, your sewer pipes can have mud and debris running along with the property. This means these things from mold to algae to roots won't go away without thoroughly cleaning your drainpipe. Good sewer cleaning should be a two-step process. First, the cleaners has to clean the drain completely, then the contractor has to show you with the help of a camera that the drain is 100% clean. A professional stormwater sewer cleaning service should verify that the job you have requested has been completed.
A mechanical snake or shear is a more common solution. Most plumbers have this tool and this method is the traditional way to clean it. The problem with this solution is that the process simply cuts a hole in the plug instead of removing all the debris.
On the other hand, hydro jets use small amounts of water at very high pressures to clean the walls of your pipes, including storm sewers and gutters. The hydro-jet cuts roots, all dirt, and grease, and causes blockages completely removed from the inner walls. At the end of the process, the drain or sewer pipe returns to its original diameter.
At the end of the process, the camera is a very simple and inexpensive test. A reputable company will offer this as part of their service and will have the tools to quickly show you what your sourcing is like.