Iron Staining or Pink Slime?

Almost everyone has noticed that pink or red slime slime that forms on wet surfaces or near the water line in their toilet.  Whether its a dog bowl, faucet, shower doors and tiles, or bathroom floors, they are susceptible to this phenomenon.  But what causes it?  While dissolved iron can cause similar staining, this mysterious staining more often than not is the result of a naturally occurring airborne bacteria, Serratia marcescens, growing on surfaces that are regularly moistened that produce a red pigment called prodigiosin.


Iron staining will generally occur at and below the water line and present as more orange in color.

Pink staining from airborne bacteria will generally occur at the water line and present as more pink in color.


This type of bacteria is mostly harmless and thrives in bathroom environments and is not a result of your water chemistry.  Serratia marcescens requires almost nothing, in terms of nutrition, to survive and can cause staining nearly all year.  During periods of warm weather, when windows and doors are left open, many homeowners will reports seeing this staining occur more often and is a direct result of the airborne bacteria.  This staining will also present itself after new construction or remodeling activities in homes.  In terms of water treatment, there are no options because the bacteria is not a result of poor water quality.  The staining can be removed through scrubbing with bleach or a mixture of baking soda and water.  If there are concerns of iron in your water,  Master Water Conditioning can provide a free analysis. Click here for more information.