RESIDENTIAL GAS AND ELECTRIC WATER HEATER
SERVICE HANDBOOK
A.O. Smith Water Products Company
Training Department
©
2002
Ashland City, Tennessee
53
TECHNICAL BULLETIN
BULLETIN 22
SMELLY WATER
CAUSE
The most common cause of “smelly water” is a non-toxic sulfate reducing
bacteria, scientifically termed
Divibrio Sulfurcans
. This bacteria often enters
the water system through construction or a break in ground piping. The
bacteria creates the energy it needs to survive by converting sulfate (SO
4
) to
hydrogen sulfide (H
2
S) gas you smell in the water.
Hydrogen sulfide gas is distinctive because of its rotten egg-like stench. Its
presence can severely affect the taste as well as the odor of the water.
Occasionally this bacteria can be accompanied by black deposits, the result
of pipe and fitting corrosion. In extremely high concentrations, hydrogen
sulfide gas can be toxic though the gas is detectable long before harmful
levels are reached.
The requirements for the bacteria to thrive are: a) an elevated level of sulfur in
the water, b) activated hydrogen from cathodic reactions within the tank, c)
water with little or no dissolved oxygen, d) and temperatures below 138
°
F.
Items that can increase the potential for this bacteria are: a) water softeners,
b) well water, c) and long periods of no water movement.
Other factors that may contribute to smelly water:
•
Chlorides of Magnesium and Calcium leave a bitter taste.
•
Chloride of Sodium produces a salty taste.
•
Sulfates (50 ppm) give a medicinal taste.
•
Carbon Dioxide in a low pH water gives fizzy water.
•
Iron and tannic waters also give a bad taste and odor.
TREATMENT
The simplest treatment available is the shock-chlorination of the system. This
is a surface treatment, and often requires repeated trials in heavily infected
systems. The chlorination of a system requires that you follow each step
explicitly to avoid an un-treated portion of the piping system from reinfecting
another part. See Bulletin 23 for the chlorination procedure. Longer lasting
solutions include chlorination or aeration of the water supply.
NOTE
Since smelly water is caused by a bacteria presence and is not caused by the
water heater, any treatment would not be considered warranty related.
