The break has left 16th and Walnut Street shut down and officials announced Sunday that the street could remain closed for much of the week.
PWD says a 12-inch main broke around 3:30 p.m. Saturday in the heart of the highly populated area.
Water department crews worked for hours Saturday night along Walnut digging away to repair the water main.
Holiday shoppers were out and about, along with tens of thousands of tourists in town for the Army Navy game for a night on the town.
A water main break in the heart of Philadelphia is the last thing this city wanted to see.
"It is just a big headache in addition to all the holiday congestion around here," said Jennifer Ouarri.
Drivers made their way through flooded streets before Philadelphia police blocked off the impacted area in Center City's prime business district.
"We were in Brooks Brothers and the manager said he just saw a wave of water coming toward the store," said Kelly Lange.
Several stores including Apple were forced to close when water came right to their doorsteps.
There are no reports of damage but managers say they will suffer a loss in the registers.
"With the water on the streets, no one has been around. People got a lot of hours cut," said Matt Montrose.
In the past few months, there have been several water main breaks in the city.
In October, a 36-inch main broke at 3rd and Walnut in Old City, and back in July, a 4 foot wide main ruptured, shutting down 21st and Bainbridge for months.
Those mains were much larger compared to the one on Walnut Street Saturday night, but the location and timing definitely caused some big problems.
"We have a water main break almost every day, and as we get into the colder weather with the water temperature decreasing in the 40 degree range, we can have several breaks a day," said Debra McCarty from the Philadelphia Water Department.
Some residential buildings and businesses in the area lost water service, but service has been restored to most of those customers.