The sink is undoubtedly the workhorse of the kitchen. Think about all of the food debris and grease you put down there on a weekly basis. It can quickly accumulate and cause some pretty bad smells. Not all stinky sinks are food-related, though. You may have a plumbing issue and a potential health risk on your hands.
Is It Food or Something Else?
Food smells can be rotten and mask the scent of more serious problems. Grease and oil can coat the inside of your pipes, trapping food particles that should be flushed out. Try these methods to clean out the drain and disposal.
Hot Water and Dish Soap
Plug the sink with a stopper and fill it at least halfway with hot water. Squirt some dish soap in and pull the plug. Turn on the disposal while the sink drains.
Baking Soda and Vinegar
Pour one cup of baking soda into the drain, followed by the same amount of vinegar and let sit for 10 minutes. While you are waiting, boil a pot (about six cups) of water. Pour the boiling water down the drain to help move along any residual particles.
Citrus Peels, Ice and Salt
Throw a few ice cubes and a handful of kosher salt or another coarse salt down the drain and run the disposal for 10 to 15 seconds. The ice and salt will scrape any bits of food off of the blades and sides of the disposal. Follow this up by placing a couple of citrus peels in the disposal and grinding them up for a deodorizer. Make sure to run the water while you grind the citrus peels so you don't end up with more stuck-on food debris in your garbage disposal.
Once your drain is clean, if the smell persists, you probably have a plumbing issue.
The plumbing in your house is designed to contain harmful gases, flush away sewage, and provide you with clean and potable water. If you are smelling sewer gas in your kitchen, something has gone awry with the system. This is not only irritating, but it can also be a health hazard. Sewer gases are toxic and should not be breathed in for long periods or by those with compromised immune systems.
The P-trap is the curvy part of the pipe under the sink that resembles a "p" or a "u". It isolates the drain line from the fixture, which blocks irritating smells. The trap under an individual fixture works by holding water at the bottom of the curve to block the smell. If the P-trap is dry, it would cause a sewage smell to emanate from the sink. If the sink is in regular use, you can eliminate evaporation as a cause of the smell.
There is a small cap at the lowest point of the curve that allows you to check for blockages and clear them up if found. Clear the blockage and run the water for a few seconds to fill the trap back to optimal levels.
The connections on either side of the P-trap are easy to remove. Unscrew the connections and remove the P-trap. Remember that it may be full of water! Inspect the pipe for a leak, and give it a good clean while you have it out. If you find a leak, take careful measurements, write them down, and make sure to get the exact same size replacement trap. If you haven't found a leak using this method, replace the P-Trap, and move on to the next potential cause.
Every house has at least one main vent that exits through the roof. Most local codes dictate this to have a diameter of at least four inches, and all fixtures are supposed to be vented. This allows for the air in the piping to "vent," so the water can move through the pipe freely. If the vent is clogged, it can slow the water from draining properly.
If the sink drains slowly after trying the techniques above, it may be time to have the drain snaked by a professional.
Hydrogen Sulfide. Centers for Disease Control and Prevention.