Workers closed off the street while they capped the leak and began excavating.
Durham County Manager Michael Ruffin said the Administrative Complex was without running water and there was no way to flush toilets - prompting him to send workers home.
Authorities told employees and customers at the complex to use caution when using tap water at the facility after the water main broke.
By Tuesday evening, the pipeline to the building had been pressurized and disinfected and service to the building was fully restored. The building is expected to be open on Wednesday.
Officials are telling people to flush faucets and fountains before drinking the water.
The Administrative Complex is home to the Register of Deeds, Tax Administration, County Manager, County Attorney, Clerk to the Board, Human Resources, Budget and Management Services, Finance, Information Technology, and SAP Shared Services offices.
Durham streets were back to normal around 5:30 p.m. on Tuesday.