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I have a few tips to keep your garbage disposal clean and smelling good.
One solution is to run the unit longer with cold water running at full pressure. When you use the disposal to grind up food scraps, it is chopped into a mush that can stick to the sides of the garbage disposal. If you don't allow the unit to run long enough, this food gets caught and starts to decay, causing odor. Over time it can create a build up that is difficult to remove.
When you are doing dishes, plug the drain above the garbage disposal and let it fill with water and soap. When you drain the sink, turn on the unit so the soap can loosen built up debris.
You should grind ice cubes a couple times a month in the disposal to clean off the blades and remove debris. A great tip is to freeze some white vinegar in your ice cube trays and grind them up in the unit. This will clean and deodorize the disposer.
Grinding up small chicken and fish bones will also create a scouring action that cleans off the blades and the inside walls of the unit.
Grinding lemon and orange peels will also remove some odors and the acid in the fruit kills some odor causing bacteria.
If you use baking soda to remove odors in your refrigerator, you should dump the container into the garbage disposal, add a cup of white vinegar and turn on the unit for a few seconds. Turn it off as it starts to fizz up and let it set for 30 minutes. This is an excellent all natural way to clean and deodorize.