The water supply to about 300 commercial properties and homes in Cardiff Bay has been returned to normal after building workers hit a water main.
Welsh Water said the incident at Harbour Drive near Mermaid Quay had caused "a significant problem."
Water supplies were restored by midnight, a spokeswoman said.
A number of restaurants and bars in Mermaid Quay did not open on Friday night.
Some commercial premises had no water and some residential areas were affected by low pressure.
The burst was at a building site off Harbour Drive near the Norwegian Church.