The pink/red/orange discoloration that you see on bathroom fixtures, grout, and shower curtains come from a biolm of the bacteria Serratia marcescens, and often mistakenly called “pink mold”. It prefers areas that are moist, such as a shower. Serratia feeds on mineral deposits, toothpaste residue, and soap scum. Serratia is an airborne bacterium and cannot survive in your water supply.

The biolm of Serratia marcescens can be removed with a little elbow grease. Professionals like Bob Villa recommend mixing a quarter-cup baking soda and a tablespoon of liquid dish soap. Using a soft bristle brush, so not to scratch the surface of your fixtures, loosen the patches of biolm and rinse them away. You should take precautions to minimize your exposure to the bacteria by wearing gloves and protective glasses.

It is not enough just to scrub away the biolm. The area must also be disinfected to kill any remaining bacteria colonies to prevent it from reestablishing. An antibacterial cleaner with bleach is recommended for killing any bacteria left behind. Spray the cleaner on the areas and let it stand for at least 10 minutes because contact time of the bacteria to the disinfectant is key. Using another soft bristle brush, scrub all surfaces and rinse. This process may need to be repeated every few days until all the colonies are removed.