An MTA train yard in Upper Manhattan is on “fire watch” after investigators discovered the facility lacks sufficient water to power its sprinklers and fire hydrants in the event of a blaze, the MTA Inspector General said Wednesday.

Tests conducted by outside contractors in March found two fire pumps at the 207th Street Yard “failed immediately” due insufficient water levels, the IG’s office said in a report that accused transit officials of failing to conduct required annual tests on all but one fire pump at the site last year.

“Fire suppression personnel do not have the proper training either to perform fire pump tests adequately or to assess the test results correctly,” Acting IG Elizabeth Keating wrote. “There is no record that existing gauges have been calibrated or regularly replaced.”

Located in Inwood, the 207th Street Yard is a maintenance and overhaul shop for trains from every subway line in the city.

According to the IG’s office, the facility’s water supply “loops” around the yard to provide water to sprinklers and fire hydrants. IG investigators tested the water pressure in the “fire loop” and found it would be “insufficient” in the case of a fire.

Keating’s “interim report” recommended MTA New York City Transit test the water press on all 23 pumps at the yard, and advised that the authority employ an outside contractor to do so.

“NYCT must ensure they have an adequate water supply to fight fires, anything less in unacceptable,” Keating said in a statement. “The workforce reporting to the 207th Street Yard, and every other MTA facility, deserve a safe work environment.”

A spokesman for the MTA said a contractor reviewed the fire suppression systems in the last three weeks and that a “24/7 fire watch” is in effect at the two buildings where IG probers found the weak water pumps.

Authority Chief Safety Officer Pat Warren claimed in a statement “there is no known fire safety hazard.”

“There is no known fire safety hazard in New York City Transit train yards where we instituted preventative measures and had independent certified fire suppression experts assist in testing equipment and installing any necessary upgrades,” Warren said. “There can be no compromise when it comes to the safety of MTA employees and when safety issues arise we address them immediately.”