SEPTA said Section A was shut down as crews worked to clean up the flooding. Trains were running normally, but riders were rerouted through different entrances and exits while repairs continued.
"That whole section is shutoff you gotta go around," said Jude Martin of East Falls.
SEPTA said the break happened near 12th and Filbert streets. The Philadelphia Water Department said it is investigating whether the source was a city water main or a SEPTA pipe. SEPTA workers were inside Jefferson Station Monday night, helping riders navigate the disruption.
"The SEPTA team is trying to be very helpful and get me to my train, but a watermain break is just old infrastructure suffering badly," said Keith Day of Glenside.
The incident comes amid prolonged cold weather that has stressed aging infrastructure across the city. Philadelphia Water said it has responded to dozens of similar calls in recent weeks following a snowstorm and extended frigid temperatures.
"I'm in East Falls, I know there's a few frozen pipes there, Fairmount, there was a bunch of frozen pipes bursting. I don't think we've had cold like this, this long in a long time if ever," Martin said.
At Jefferson Station, SEPTA said there have been no service disruptions, but riders said planning ahead remains important.
"You gotta always check the app, make sure your trains gonna show up, make sure there's nothing crazy going on," Martin said.
It was not immediately clear when the water main break was first reported or when Section A will reopen. SEPTA said riders will continue to be rerouted as cleanup continues.