©2018 Mahoning Valley Water Inc.  Serratia marcescens      Pink residue is less likely a problem associated with water quality than with naturally occurring airborne bacteria.    The bacteria produces a pinkish film, and sometimes a dark gray film, on surfaces that are regularly moist, including toilet bowls, showerheads, sink drains, and tiles.  The problem also more commonly occurs in humid regions of the country.        Although the exact species of bacteria is not known, most experts have concluded that this pink staining is most likely from the bacteria Serratia marcescens. These bacteria thrive on moisture, dust, and phosphates and are widely distributed, having been found naturally in soil, food, and also in animals.  The conditions for the survival of Serratia marcescens are minimal, and the bacteria may even feed upon itself in the absence of other nutrients.       Members of the Serratia genus were once known as harmless organisms that produced a characteristic red pigment.  Because of this, scientists and teachers frequently used it in experiments to track other microbes.  More recently, Serratia marcescens has been found to be pathogenic to some people, having been identified as a cause of urinary tract infections, wound infections, and pneumonia, and is no longer recommended for use in school experiments.      Many times, the pinkish film appears during and after new construction or remodeling activities, or during warm months when windows are left open for extended periods of time.  Once airborne, the bacteria seek moist environments to proliferate.      The best solution to keep these surfaces free from the bacterial film is continual cleaning.  A chlorinous compound is best, but use care with abrasives to avoid scratching the fixtures, which will make them even more susceptible to bacteria.  Chlorine bleach can be stirred into the toilet tank and flushed into the bowl itself.  As the tank refills, more bleach can be added.  Three to five tablespoons of bleach should be all that is necessary.  A toilet cake that contains a disinfectant can keep a residual in the water at all times.  The porous walls of a toilet tank can harbor many opportunistic organisms.      Cleaning and flushing with chlorine will not necessarily eliminate the problem, but will help to control these bacteria.  Keep bathtubs and sinks wiped down and dry to avoid this problem.  Using cleaning solution that contains chlorine will help curtail the onset of the bacteria. MAHONING VALLEY WATER