Drain Odors and What is Causing Them

There it is. The undeniable stench coming from the sink. The immediate response is to go for the cleaning products, but they only help in some cases. Depending on the situation, cleaners may not help at all. Drain odors themselves may be able to diagnose the problem, but it may not always be that easy. The drain in which the odor is coming may also be able to signify its origins. Other times, you may just want a professional opinion from someone that can help you fix your drain odors. To be safe, drain odors should be fixed sooner rather than later because some odors may be toxic.

In the following paragraphs we will discuss some potential causes and solutions to the smell in your drain.


After you have noticed drain odors, you may have snaked it yourself and seen the black slimy gunk that comes out. That is biofilm. Bacteria builds up on whatever is trapped in your drain and begins to smell. The hair and food become the perfect breeding ground in a warm damp environment. Snaking is an option to remove blockages that hold the bacteria. You can also use remedies like boiling water or a mixture of vinegar and baking soda to kill the bacteria and eliminate odors.


If your drain smells like sewer gas, it may be an indication of a problem. The P-trap is designed to not let sewer gases out beyond the waterline. The gas you are most likely smelling is hydrogen sulfide. It has a distinct rotten egg smell and can be dangerous if you are exposed to a lot for a long period. The smell is probably not immediately dangerous, but it is recommended you treat the problem quickly. The P-trap in your drain holds water and does not allow the sewer gas to make it past the bend in the plumbing. Smelling sewer gas may indicate that the P-trap is dry, or worse yet, a sewer backup. In either case you will have to call in a plumber to fix the problem.


Clogs cause drain odors by backing up sinks, showers, and toilets. They begin to smell when whatever is causing the block begins to decay or collect bacteria. We want to mention clogs separate from bacteria because this is especially a problem for kitchen sinks. When food starts to clog in a sink, they begin to rot like they would anywhere else. The problem is you can’t take the trash out to get rid of the stink. If it is a bad clog; boiling water, snakes, and vinegar may not be able to cut it. In this case, you should call a plumber. They have the proper tools to do the job.

Water problems

Sometimes it might just be your water that is causing your drain odors. This can be the case with well and public water. Hydrogen sulfide gas (which we discussed in our sewer section) can also occur in water wells. The gas can be naturally occurring or caused by chemical reactions, bacteria, decay, or pollution. If you notice a rotten egg smell coming from your water, not your drain, then you should have your water tested. It is important to test for harmful bacteria in your water supply as well as other contamination like metals and chemicals. Chlorine treatments and filtration can often help well water. Public water may also be inadequately chlorinated. This can also lead to bacteria growth in your water. This should be dealt with by contacting your water supplier. Valley can assist with water filtration options to fit your specific commercial or residential needs.


Colonies of mold can grow in and around your drain. Because mold is alive, they produce smells during the processes of digestion and reproduction. In this case, what you are most likely smelling is the musty smell of mold spores released from a colony. Inhaling these spores can be extremely dangerous. I am sure you have heard some of the horrors of black mold. Exposure to the spores can lead to a variety of symptoms reminiscent of asthma or severe allergies. If the area of the mold has not spread too drastically you may be able to clean it yourself. However, if you have a large area affected by mold or if it continues to smell after you have cleaned it, it is best to hire mold removal experts.

Typically, you do not want your drain to smell like anything. If you start to notice a smell, diagnosing the problem is the first step. If you are not confident in your ability to tell what the drain odors are or where they are coming from, a plumber is a great option to find and eliminate the unknown cause. Many times, home remedies can only fix the symptoms for a short time.

At Valley Fire Protection and Plumbing we have expert plumbers that can help you get to the bottom of that smell and get rid of it for you! Call us today and be on your way to a fresh smelling drain.

Related Topics: Drain Odors // Residential Plumbing // Sewer
By: Tom Hartel
I acquired my expertise by directing day-to-day operations of the business for over 20 years. Continuous hard work helped me become a nationally recognized speaker and expert on fire protection, fire sprinklers, special hazards, and plumbing systems. In this blog, I share my knowledge that will hopefully help you make better decisions for your projects.



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