What is the pink substance from my water?

Each year, a few Mukilteo Water and Wastewater District customers call to ask about a slimy pink substance that sometimes forms in moist areas around their homes.  They most frequently observe it in toilet bowls, on the surfaces in shower stalls and bathtub enclosures, in sinks, and in pet water dishes.

A red or pink pigmented bacteria known as Serratia marcescens is thought to be the cause of pink stuff.  Serratia bacteria are common inhabitants of our environment and can be found in many places, including human and animal feces, dust, soil, and in surface water.  The bacteria will grow in any moist location where phosphorus containing materials or fatty substances accumulate.  Sources of these substances include soap residues in bathing areas, feces in toilets, soap and food residues in sinks, and food residues in pet water dishes.  Serratia can also grow in tap water in locations such as toilets in guest bathrooms where the water is left standing long enough for the chlorine residual disinfectant to dissipate.  Serratia marsescens is not known to cause any waterborne diseases.

Once established, the organism usually cannot be eliminated entirely.  However, periodic and thorough cleaning of the surfaces where the pink slime occurs, followed by disinfection with chlorine bleach appear to be the best way to control it.  Scrub the surfaces where phosphorus and fatty substances, or the bacteria accumulate with a brush and a household cleanser.  Then disinfect the surfaces where the slime has formed with a strong chlorine bleach solution.  Leave the disinfectant solution on the affected surface(s) for 10 to 20 minutes before thoroughly rinsing it away with clean water.

To control pink “stuff” in toilets, clean the bowl thoroughly and spray chlorine bleach into the bowl and under the bowl rim.  Also add ¼ cup of bleach to the toilet tank.  Let the bleach stand for 15 to 20 minutes. After 15 to 20 minutes, flush the toilet a couple of times to rinse the disinfectant out of the tank and the bowl.  Whenever a pink film starts to reappear, repeat the cleaning and disinfection process. Note: Bleach should not be left in the toilet tank for prolonged periods; it will damage the rubber valves and seals inside.

Show All Answers

1. What is the pink substance from my water?