You’ve probably run into this scenario before: you walk into the kitchen or bathroom and your senses are attacked by an unidentifiable odor. You look around for something rotting or you take out the garbage to see if that is the culprit… finally, you make your way to the sink and the smell is stronger. You start running the water to try and wash out the smell, and if you’re in the kitchen, you run the disposal thinking perhaps there is some old food in there, but that is not the case: you, my friend, have smelly drains. I am often asked how to remove the odor, and there are many possible causes and options for freshening things up.

What causes drain odor?

Clogs and bacteria – Hair, food, the substance that is scientifically referred to as “gunk,” grease and other debris can become clogged in pipes where bacteria builds up, and an odor is released.

Sewer smells – Sometimes sewer gas can rise up through the drains if there are empty drain traps. This happens more commonly in drains that are not used very often. You should also check to be sure that you don’t have a natural gas leak.

Pipe blockage – Drain pipes and sewer vent pipes can become clogged. Check to see if, when running water, it eventually stops draining and starts to pool in the sink. If there is an odor that comes up with it, you likely have a sewer pipe blockage.

Water issues – Sulfates in the water can cause water to smell. A lot of times this happens with hot water heaters when sulfate-reducing bacteria enter the system and react with the sulfates in the water heater. This is characterized by a rotten egg smell.

Mold or mildew – Mold and mildew can build up if there is even the smallest leak in a pipe underneath a sink or even behind a wall.

Plumbing error – Sometimes mistakes are made and missing traps or vents can cause a smell. Leaks and rotting drain tubes are things that can cause odors in the drain as well. 

How do you get rid of the odor?

Eliminating odor caused by clogs, pipe blockages, and bacteria – You can plug the sink, fill it with hot water, add bleach and then let it go down the drain. The bleach will kill the bacteria. Boiling water alone poured down a drain, a little bit at a time, can also help to get rid of odors caused by bacteria. A third option is to mix equal parts of vinegar and baking soda. When it starts to fizz, you can pour it down the drain, then follow it with hot water and let it sit for at least an hour. This is a great solution that is a little less harsh than bleach.
You can also snake your drain with a snake purchased from a hardware store, or even just a coat hanger to move out anything that could be clogging things up.

Fixing sewer smells and empty drain traps – The drain traps need to have water in them to keep sewer gasses from rising up. If you keep water running through your pipes, including the shower and toilet, it should help keep the traps full.

A little bit of mineral oil can be poured into drains that are not used often to help slow the evaporation of water out of the traps.

Fixing plumbing issues and leaks causing mold and mildew – These issues will require a good plumber. Have them check and fix traps and vents and add or replace them if necessary. The plumber should also check for leaks and other issues that may be causing odor and then make the proper repairs so that it is no longer an issue.

Fixing water issues – Simply turning up the heat in the water heater to kill the bacteria can fix this problem. The standard setting is 140 degrees F, which should kill bacteria, but increasing it to 160 degrees for a short amount of time should ensure that the sulfate-reducing bacteria are eliminated. Flush the water heater by running the hot water for 10-15 minutes, preferably in a bathtub. If this is done to fix these issues, make sure that there is a pressure release valve on your water heater first or this could put you in danger.

Nobody enjoys drain odor, and there are a number of things that can cause it. The good news is there are many options for treating the smell that are low-cost and effective. Bigger issues should be solved by an experienced plumber, but it’s always a good idea to test out and try the do-it-yourself methods if you can.