Dunedin City Council water and waste group manager Laura McElhone said it was believed plummeting overnight temperatures caused the main on the corner of High and Princes Sts to burst about 2.30am.
The council was alerted to the problem following a call from
a member of the public reporting water on the footpath, she said.
The water was turned off at 4am, cutting supply to businesses on the west side of Princes St from High St to Manse St, as well as the South side of High St, from Princes St up to Clark St.
New Zealand Fight and Fitness Academy gymnasium owner Ryan Henry said his business had been disrupted by the outage.
"No-one came up to tell us the water wasn't running.
"There was a class at 6.30am and when people went to have a shower ... they couldn't.''
The outage also affected Mr Henry's lunchtime classes.
Galloway Cook Allan receptionist Sophie Borland said the outage had rendered four bathrooms unusable, leaving one functioning toilet for 50 staff.
Dr McElhone said the council did its best to minimise interruptions to water supply.
However, uninterrupted supply was not guaranteed and affected businesses would not be compensated.
The water was turned back on at 1pm.