There are currently 19 Con Ed steam pipes leaking under our feet, the utility said.

A section of its 105-mile underground network ruptured in the Flatiron district on July 19, spewing asbestos into the air and forcing the evacuation of nearly 50 buildings.

The cause of the explosion has not been established. A blast near Grand Central Terminal in 2007, which killed a passer-by who suffered a heart attack, was blamed on cool water hitting the steam pipe and causing a rapid pressure change inside it.

“To lose a line in the middle of Fifth Avenue, that’s inexcusable,” said William Byrd, an engineer and founder of Columbia Corrosion Control in South Carolina, which specializes in pipe-corrosion work. “Someone should have been out there checking that.”

Corrosion from water eating away at the pipes is the main enemy of the system, said Michael Tobias, founding principal of New York Engineers in Midtown.

Tobias said leaks that can cause the most danger come from the rapid increase in pressure in the pipes.

Con Ed says it has 882 remote monitoring stations to keep tabs on the pressure in the steam-pipe system that runs only under Manhattan streets. Workers also visit high-risk locations after heavy storms.

“If there is a drop in steam pressure at a particular location we will send out a crew to investigate and repair if there is a leak,” spokesman Michael Clendenin said.

The steam system started operating in 1882 and pipes currently run from the Battery north to 96th Street on the West Side and up to 89th Street on the East Side.

A total of 1,630 buildings use steam for heating and cooling, including Grand Central Terminal, the Empire State Building and the United Nations.