Most pink staining reported by customers is caused by a pink biofilm. Biofilm is typically composed of many different microorganisms and bacteria held together by biological polymers that improve the ability of bacteria to adhere to and proliferate on wet surfaces.
Unfortunately, biofilms may never be completely eliminated. So what can be done? Keep it dry. Leaking faucets provide moisture for growth. Keep it clean. Good old-fashioned scrubbing is the best solution. For more information on “pink stain” go to (www.awwa.org).