Preventive flushing of the sewer system occurs as frequently as quarterly, depending on the area. Doorknob notices are provided in advance in the area to be flushed. In rare instances, a slight sewage odor may be detected. Should this occur, you should flush all toilets and run water in all sinks and bathtubs to ensure that water is in all of your drains. The passage of odors is impeded when water is in all drain pipe traps. In addition, we recommend that you make sure all toilet lids are closed and if there are windows in your basement, you may want to open them slightly.