Well there are several different reasons there could be a funky smell coming out of your drain in the kitchen sink.
Kitchen sink smells like rotten eggs.
Generally the smell of rotten eggs comes from a sulfurous gas that is produced from a build up of gunk hair and other particles that accumulate within the drain.
Natural gas and propane are odorless but gas companies inject them with a chemical called mercaptan that gives them a sulfur smell like rotten eggs to alert residents to a gas leak.
One of the most common reasons for a kitchen sink to have a rotten egg or moldy smell is from grease or fat getting stuck in your drains.
It is likely the odor is coming from the accumulation of bacteria at the end of the sink s overflow hole.
The following is an easy inexpensive and very effective solution.
If the sink smells like rotting food then you have a build up of food fats and oils in your pipes.
Another possible reason for the rotten egg smell in your bathroom sink is outgassing.
You must check if the smell is coming from the water or the drain.
If the sink smells like rotten eggs you have sewer gases escaping into your home due to a problem with your u bend.
Lots of things can get stuck in the trap of the kitchen or bathroom sinks and when those things start to decompose it can make the drain breathe out a horrible rotten egg smell.
You may have noticed a foul sewer like odor from the small overflow outlet hole in your bathroom sink.
When you pour grease down your drain it can congeal to the sides.
And then as it begins to decompose the smell can make its way back into your home.
This gas usually smells distinctly like rotten eggs and can be pretty overpowering.
Hydrogen sulfide distinguished by a rotten egg odor causes yellow or black stains on fixtures.
It affects the taste and smell of coffee and food.
So don t put grease down the drain.
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These smells are not uncommon but need to be dealt with to make your kitchen usable again.
Although hydrogen sulfide is flammable and poisonous it is usually not a health risk at the concentrations found in household water.
Most of the time you will immediately identify the smell as coming from either rotten eggs or something else rather sulfurous.