It happened on Jerome Avenue and East 177th street in Mount Hope Wednesday morning.
The streets are dry now, but big problems remain. There are ongoing bus disruptions, and 500 mom-and-pop shops and residential gas customers are waiting on Con Edison to hook service back up.
Officials say all utility lines, including phone service, were affected in some way. And there's a 6-foot deep crater in the middle of the street and 12 blocks of water damage to repair after the geyser-like break turned one of the Bronx's busiest streets into a bubbling river.
"We're surrounded by water," resident Raymond Ortega said. "We can't go nowhere. We can't get nowhere. We're stuck."
The break in the 108-year-old main sent tens of thousands of gallons of water gushing along Jerome Avenue. It took crews nearly three hours to shut it off because that main supplies water to the entire city.
The entrance to the Cross Bronx Expressway had to be shut down, and No. 4 subway service was stopped in its tracks for hours.
A day later, Jerome Avenue remains closed, littered with soggy debris dragged from flooded basements. People spent the day cleaning up and adding up their losses.
"I have $50,000 in damages," business owner Michael Montas said.
But the biggest problem, aside from all the water damage, is that Con Ed has to go door to door to restore gas service to those 500 homes and businesses.
And still, no one knows what exactly caused the century-old main to break.
"We need to investigate this," New York City Department of Environmental Protection Cas Holloway said. "Age in and of itself is not a reason why a main of this size and strength would break. We'll have to see."
Service on the BX32 and BX36 bus lines remains detoured.