A pink film or residue on bathroom and kitchen surfaces generally does not indicate a problem with water quality. In fact, the pink residue is likely a result of airborne bacteria present in the home that produce a pinkish or dark gray film on surfaces that are routinely moist such as toilet bowls, showerheads, sink drains, and tiles. Some people have reported that the pink residue appears in their pet’s water bowl and fortunately it has not caused harm to the pet and is easily cleaned off.
Many experts agree that the bacteria that causes this pink film is most likely Serratia marcesens, a bacteria which is found naturally in soil, food, and in animals. Serratia, which produce a characteristic red pigment, thrive on moisture, dust, and phosphates and need almost nothing to survive. Generally thought to be harmless, recently Serratia marcesens has been tied to urinary tract infections, wound infections, and pneumonia in some people.