The MTA has shelled out around $5 million in the past year for workers to patrol a Brooklyn bus depot on the lookout for open flames — because its sprinkler system is on the fritz, agency sources said Monday.

The millions of dollars in spending on an employee-fueled work-around for a decrepit broken system comes a day after the Metropolitan Transportation Authority jacked up its bridge and tunnel tolls and two weeks before it increases its subway and bus fares.

“Following the repairs of sprinkler system leaks at the depot in June, crews conducting a test of the system discovered additional leaks,” MTA spokesman Michael Cortez told The Post in a statement.

“As a result, the MTA will pursue a more comprehensive project to make repairs to the facility, which will include a temporary relining and then a longer-term solution,” Cortez said.

Meanwhile, as many of 30 people a day have been assigned on overtime to toil the ’round-the-clock fire watches, or 10 people per shift, at the East New York bus depot for the past year — work ordered since the agency discovered the complex’s pipes can’t maintain enough water pressure to make the system work reliably.

A source said the fire-watch shifts pays employees $60 an hour, which pencils out to roughly $5 million a year.

“The pipes are really old,” another source said. “The answer is to rip everything out.”

The second person estimated it would cost “millions and millions and millions” to redo the facility and added it is possible the MTA decided that eating the OT amount would cost less than an overhaul for now.

The MTA confirmed that 10 people are assigned to each shift and estimated that to replace the sprinkler system would run into “the millions” but declined to comment on the other figures, including the total price tag for the extra shifts.

The chief of the MTA’s city transit division, Rich Davey, offered reporters a more optimistic assessment last week when he was quizzed about the ongoing fire-system snafus.

“We expect it to be working, we expect, within weeks,” Davey said before adding, “We continue to look at the underground pipe, and each time we get it pressurized, there’s a bit of a challenge.

“We’d rather have a working fire suppression system than having to pay a 24-hour fire watch,” he acknowledged.

Documents with a partial accounting of the overtime cost previously showed the figure was at least $2.4 million, according to a report published in the New York Daily News.

East New York is not the MTA’s only facility to struggle with malfunctioning fire-suppression systems, a recent report from the agency’s Inspector General shows.

The watchdog’s December 2022 report revealed that the fire-suppression systems at the 207th Street train yard went without a required Fire Department inspection for 12 years.

The sprawling East New York bus depot located near Broadway Junction has received millions of dollars in other upgrades in recent years, according to agency documents.

There is currently an $18 million effort to fix its brick façade and replace its exterior windows. Another $12 million is set to be spent on replacing the heating and air conditioning systems beginning next year.

That work is on top of the $4.3 million the depot got to replace portions of its ventilation systems in 2014.

Three bus depots were slated for fire-alarm-system replacements in 2018 — but the East New York depot was not one of them, MTA budget records show.

“There is no higher priority than the safety of the people who move millions of New Yorkers daily,” Cortez said.