If you have a nasty smell originating from your waste disposal unit, this is due to food particles buildup. You have to put ice, orange peels, and lemon peels into the disposal and run for about 30 seconds. Next, run some liquid dish soap through the disposal. This must look after the issue if there is not a substantial blocking accumulation.
Make use of a foaming root killer, twice annual, to eliminate tree roots that can bring your drains to a standstill. Lathering items fill the whole pipe with chemicals, eliminating roots that grow from the top of the pipe in addition to the part that water streams through. They are more effective than regular root killers for this reason.