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 blocks sewer gases trying to travel inside your house from the exterior systems. It works by holding water at the bottom of the curve to block the gases from going the wrong way. If the P-trap is blocked, or 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, so it is either blocked, or there is a leak preventing the water from getting to the bottom of the trap.
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 a plumbing vent sticking out of the roof. This is a long, narrow vertical pipe that connects your main sewer line to the outside air. They replace the air that is flushed down the drain with fresh air. If the vent is clogged, sewer gas can get into the house. You can clean it out yourself if the obstruction is easily visible. If you can't see it, a professional plumber can run a smoke test and find the obstruction in no time.