Officials said Tuesday that residents of Hamilton and Hopewell townships no longer need to boil water before drinking.
The advisory remains in effect for residents of the city of Trenton and Ewing and Lawrence townships.
The boil-water advisory was issued Monday for five communities because Trenton's water plant has experienced problems treating water due to the high level of the Delaware River.
The water level in the Delaware is unusually high after last week's torrential rains.
Officials did not say when the advisory might be lifted for the remaining three communities.
Trenton Mayor Tony Mack has apologized for the situation, saying workers are on the job non-stop to resolve the problem.
A city health official said that, if you drank the water, you only need to worry if you feel ill. You should then see your doctor.