But often some is left behind. Over time a thick layer of slime starts to collect on the inside surface of this vertical pipe. Because of the fixed metal parts at the bottom of sink and tub drains, it is virtually impossible to completely clean these pipes while they are in place. Often you can take apart the drain assembly and clean the inside of this pipe in a jiffy. Pay attention to the rubber washers and gaskets as you take them apart.
Bathroom sinks can also develop odors in the overflow part of the actual sink.
The overflow is a little hole at the top of the sink that connects to the bottom of the sink. It is also susceptible to slime buildup. If you are on a city sewer system, you can try to pour a 50-50 mix of chlorine bleach and water into this hole. A turkey baster works well for this purpose. Never mix chlorine bleach with ammonia or other cleaning liquids.