The city of Portland decided to discard the water after a 19-year-old man was videotaped urinating into the reservoir.
Portland Water Bureau spokesperson Jaymee Cuti said on Thursday that test samples of water taken from the reservoir came back clean.
Though acknowledging the urine posed little risk, Portland officials said they have plenty of water to meet demand and didn't want to deliver deliberately tainted water to customers.
The teenager was cited for trespassing and public urination. The Multnomah County District Attorney's Office will decide whether to pursue criminal charges.