In most parts of the U.S., we’re privileged to have access to clean drinking water with a simple turn of the tap. Sure, we may use a filter for a smoother taste. But by and large, our tap water feels safe.However, a 2018 study about how bacteria grows in plumbing systems conducted by the University of Illinois at Urbana-Champaign\u00a0reveals there could be something lurking in our H2O that wasn’t previously detectable.Bacteria in Tap WaterResearchers found bacteria in tap water can actually proliferate if a faucet has gone unused for a few days. What kind of bacteria, you ask? According to the University of Illinois study, the same microbial communities associated with such illnesses as Legionnaires’ disease.Before you vow to never use your faucet again, first understand this: Plenty of innocent microbes already live in our tap water. Researchers attest that the bacteria found in the study don’t appear to present a health risk, no matter how icky the thought of it might sound.Collecting Tap Water SamplesIn their research, the study authors took tap water samples from three dormitories on the University of Illinois campus before the school closed for a break, and then again just ahead of the students’ return.“Our results suggest that the increase in bacteria in the post-stagnation samples is a result of something occurring in the interior plumbing, not the outside city source, and in pipe segments closest to the taps,” Wen-Tso Liu, a civil and environmental engineering professor who co-authored the study, said in a press release.Running Your Water Before Filling Your GlassResearchers believe that the influx of bacteria in the post-stagnation samples is due to the interaction between the biofilm on the inside of plumbing pipes and the tap water. They also learned that bacteria was heaviest in the first 100 milliliters of flowing water once a faucet had gone back into use after a period of rest.With that in mind, if you’re returning from a vacation or weekend away, Liu suggests running your faucet for a minute or two before filling your glass.“It is contrary to what we have learned about conserving water, but I like to think of it as just another basic hygiene step,” he says. “We have made a habit out of washing our hands; I think we can make a habit out of running the tap for few moments before use as well.”Up next, check out these 100 plumbing goofs and other plumbing mix-ups.