Drain odors are a common problem in
many homes and are typically noticed when running the water in a
sink, shower or bathtub. Initially it seems that the water
stinks, but a little detective work and proper knowledge will
help you discover and eliminate the source of the odor.
To determine where the smell is
coming from, plug the drain before running the water, so your
nose is not already filled with the odor. Now turn the water on.
If you don't detect the smell, then the culprit is probably a
combination of rotting, mildewing dirt and hair debris lodged in
the P-shaped trap under the fixture and a buildup of a
bacteria-filled slime layer (biofilm) on the sides of the
vertical drain pipe. As water rushes past the slime and debris,
odor-causing molecules dislodge and drift up out of the drain
into your nose.
eliminate the odor's source, remove the strainer cover from the
shower drain or the stopper mechanism from the sink drain so you
can see into the drainpipe. Use soap and water and a
larger-diameter bottlebrush to thoroughly clean the underside of
the strainer, the stopper mechanism, the drain assembly and the
sides of the vertical drainpipe, then rinse thoroughly with hot
water. In addition, pour a solution of one or two parts
household bleach to 10 parts water into the drain and let sit
overnight to kill the odor-causing bacteria. The bleach solution
is also helpful if the drain cover or
stopper mechanism cannot be removed.
If you don't like using chemicals,
have a septic system, or are cleaning a garbage disposal drain
that can be damaged by bleach, consider this natural drain
cleaner. Pour 1/2 cup of baking soda into the drain followed by
1/2 cup of white vinegar. The baking soda is basic and the
vinegar is acidic, so they will react with a churning action
that will help clean the drain.
Also, if a sink or shower is used
infrequently, the water in the P-trap below the drain can
evaporate allowing sewer gasses to come up through the drain
into your home. To prevent this from happening, make sure the
trap never dries out by periodically running water in the sink
Does your hot water smell?
Even though the City of Mesa chlorinates every water source
before it enters the distribution system, sulfur or "rotten-egg"
odors can develop in water heaters. Incidences of these odors in
hot water are primarily due to the presence of sulfates and
their reaction with sulfate-reducing bacteria that can thrive in
the conditions provided by a water heater. The odors may occur
due to one or a combination of the following factors: setting
the water heater temperature too low and/or inactivity during
vacations when the water sits for days, weeks or months.
Despite the offensive odor, the
presence of sulfates at levels detected in the City of Mesa's
drinking water and the sulfate-reducing bacteria living in the
water heater are not harmful to your health. This simple test
will help you determine whether the odor is coming from the hot
or cold water:
Cover the drain (odors commonly
occur in the drain pipe) and run the hot water. Note if you
detect the rotten-egg odor. Next, move to another faucet in the
house, cover the drain and run the cold water. If the cold water
has an odor, please contact the City of Mesa Water Quality
Services for further assistance. If you determine that the odor
is only in the hot water, then it is most likely originating in
the water heater.
The remedy may be as simple as
killing the bacteria with increased heat. Sulfate-reducing
bacteria die at about 140 degrees Fahrenheit. Water heaters are factory
set at 140 degrees, which is the medium setting on
the temperature control dial. Increasing the temperature to the
high setting - 160 degrees Fahrenheit - for several hours should kill the
sulfate-reducing bacteria. It is just as important to then flush
the water heater to remove the dead bacteria. The fastest way to
do this is by turning on the hot water in the bathtub for 10 to
15 minutes. CAUTION: The hot water tank must have an operable
pressure relief valve; otherwise this method of treatment may be
dangerous. The temperature setting must be reduced following
treatment to prevent scalding hot water and to avoid high energy
For more information about
Please contact the Water Quality division at 480-644-6461.