About 7,000 DC Water customers in Northeast were the last to get the all-clear.
After an initial test came back positive for bacteria, further results did not show such bacteria, DC Water said.
Otherwise, water use can return to normal.
Pools in the affected areas were closed, but most reopened by Sunday afternoon.
Water taken from pipes servicing those neighborhoods initially tested positive for coliform bacteria.
Further tests confirmed the water was safe leading up to the third day of the boil water advisory, which was initially put into place Friday.
DC Water said it dropped the boil water advisory for all of the other previously affected neighborhoods because all of the tests in those areas came back negative.
It’s not confirmed that the pressure issue at a pumping station that sparked the advisory caused the possible contamination, Sweeney said.
Some residents were told their water was safe later on Friday, while many residents of Northwest and Northeast woke up Saturday unable to drink water straight from the tap.
DC Water CEO David Gadis apologized Saturday that the DC Water website went down as residents logged on Friday in search of more information about the boil advisory.