Each year, a few customers call to ask us about pink stains or residues that occasionally develop in moist areas in their homes. They generally observe this in toilet bowls, around sink and tub drains, on shower curtains or other shower surfaces, and even in pet water dishes. The customer naturally wants to know if there is something wrong with his/her water.
No, a pink residue is not a problem with your water quality, and is not harmful in this situation. It is evidence of bacteria that are common inhabitants of our environment. The most typical of these bacteria is one known as Serratia marcescens. These bacteria come from any of a number of naturally-occurring sources, such as soil, mulch, dust, and surface waters, and they thrive in an environment that is moist and high in phosphates. For instance, a pink stain or film often appears during or after construction or remodeling, when dirt and dust containing Serratia are disturbed. More people indicate the problem occurs in the summer months when temperatures and humidity are higher, and especially if windows are kept open for any length of time.
Serratia will not survive in chlorinated drinking water. However, where water stands long enough for the residual chlorine disinfectant to dissipate, such as a toilet in a guest bathroom, or on a shower curtain, the pink color may develop. Customers who remove the chlorine from their water by use of an activated carbon filter may also be more likely to experience the problem.
How Can I Get Rid of the Stains?
Once established, Serratia is difficult to eliminate entirely. However, regular and thorough cleaning, followed by disinfection with chlorine bleach, is the best means to control the organism.
- Wipe bathtubs, shower walls and curtains, and around drains in order to dry them, followed by spraying or misting with a product that contains bleach or other disinfectant.
- For toilets, clean the bowl regularly. You may wish to add ¼ cup of bleach to the toilet tank, let stand for 15-20 minutes, and then flush the bowl a couple of times to fully rinse the disinfectant. Bleach should not be left in the toilet tank for prolonged periods, however, as it will damage the rubber seals and valves inside.
- Use care with any abrasives to avoid scratching a fixture or surface, which will raise the likelihood of bacterial growth.
- Clean pet water bowls in a similar manner. Leave a bleach solution in the bowl for 15-20 minutes, followed by thorough rinsing.
- For our customers who have a septic system, consideration should always be given to the amount of bleach or other disinfectants that are allowed to enter the system.