Smelly Sink Drain


One of the most common questions I get asked by homeowners is "How come my bathroom sink drain smells so bad?". Of course it's not always the bathroom sink they complain smells terrible, it could be any household drain, but more often than not it's the bathroom sink, or shower that's the culprit.

Bathroom sink drain - chrome p-trapThe reason why bathroom drains are more likely to smell is because of the organic matter from our bodies going down the drain, which is the perfect food for bacteria. These bacteria form a slimy residue, called biofilm, along the inside of the pipe, between the trap and the fixture, which in turn helps collect even more organic matter. Since the fixture's trap forms a water seal that protect against sewer gases escaping, what your smelling is actually the decomposing organic matter on the short vertical section of pipe directly under the sink, called the fixture outlet pipe.





How to get rid of the smell

Ok, so now you know why your drain smells like a swamp, but how can you fix it? Below are some common remedies ranging from fairly simple to more involved approaches:

  • The best way (what I recommend) to get rid of the smell is to completely remove the organic matter that's trapped in the pipe. If the fixture has a removable trap, place a bucket under it and slowly loosen the threaded connections. Thoroughly clean the trap under hot water with a brush. Use a long flexible brush to clean the remaining vertical pipe that goes up to the sink. Remove any hair that is caught on the strainer.
  • Use a deodorizing enzyme cleaner. These enzyme cleaners can often be purchased at hardware stores and work by attacking the bacteria and masking the odor.
  • Fill the sink with hot water and mix in a generous amount of chlorine bleach, allow to drain and repeat as required. The chlorine will kill the bacteria but may take several cycles.
  • Some have said pouring baking soda down the drain then following that with lemon juice or vinegar has worked well for them.
  • Have another suggestion? webmaster@plumbinghelp.ca