That "pink stuff" that you may be seeing around your sink drains or in your toilets is naturally occurring airborne bacteria that has nothing to do with the quality of your water. Once airborne, these bacteria seek moist environments to grow.
Always keep bathtubs and sinks wiped down and dry. Frequently clean your sinks with a cleaning solution that contains chlorine. Three to five tablespoons of chlorine bleach can be periodically stirred into the toilet tank and flushed into the bowl itself. Cleaning and flushing with chlorine may not eliminate the problem, but will help control the bacteria growth. If you have a septic tank, use a non-chlorine cleaner, such as borax to avoid damaging your septic system.
Important! Be sure to follow the manufacturer's cleaning instructions for your plumbing fixtures and countertops; chlorine cannot be used with some designer products. Use care with abrasives to avoid scratching fixtures, which will make them even more susceptible to bacteria.