Pink stains appearing on bathroom fixtures, drainboard surfaces and pet dishes are usually from a bacteria, Serratia marcescens.

This pink residue is less likely a problem associated with water quality than with naturally occurring airborne bacteria. The bacteria produce a pinkish film (sometimes dark gray) and often appear during and after new construction or remodeling activities.

The dirt and dust stirred up from the work probably contains Serratia bacteria. Once airborne, the bacteria seek moist environments to proliferate. These airborne bacteria can come from any number of naturally occurring sources, and the condition can be futher aggravated if customers remove the chlorine from their water by way of an activated carbon filter.

The best solution to keep these surfaces free from the bacterial film is continual cleaning. A chlorinous compound is best, but use care with abrasives to avoid scratching the fixtures, which will make them even more susceptible to bacteria. Chlorine bleach (3 - 5 tablespoons) can be periodically stirred into the toilet tank and flushed into the bowl itself. Keep bathtubs and sinks wiped down and dry to avoid this problem.