Brad Destelhorst stood in the dimly lit, musty vault — a small concrete room 20 feet underground near the Capital Beltway — and tried not to think about his soaked feet, or the muddy water he stood in, or the fact that more than 100,000 people in southern Prince George’s County needed him to fix the unfixable.

For almost 12 hours Tuesday, Destelhorst and fellow mechanics for the Washington Suburban Sanitary Commission chiseled years of thick rust off gears that corrosion had frozen in place and then fashioned new gears out of the gunked-up pieces of metal.

Other crews had spent three days trying to fix the valve, hoping to head off a water outage that utility officials said would be necessary to replace part of an enormous water main on the verge of exploding. But with new parts for the 48-year-old valve unavailable, the other crews had said they found it impossible to repair.

Destelhorst, an admittedly stubborn former auto mechanic from Crownsville, wouldn’t have it. He said Thursday that he was prepared to break every tool he had to get the gears turning and the valve closed.

“No one should have to go without water,” he said.

See how your activities add up to your total water usage in a day.

WSSC General Manager Jerry N. Johnson credited Destelhorst, his partner Tommy Ecker and their colleagues with averting “a major disaster.” By Tuesday night, the team had turned the gears 400 times, successfully closing the valve and isolating a relatively short section of the damaged pipe. Rather than having to close a three-mile section, the utility had to isolate only 0.82 mile once it was able to shut the valve, officials said.

With water being diverted around a far shorter section, officials said, the system could continue to deliver it to the affected area while the damaged main was drained for repairs.

Late Wednesday morning, Johnson called off the outage. The valve had, indeed, closed, he said. The proof: Water levels in the system were rising as water was being routed around the damaged main.

“These two came forward and said, ‘Give us the ball, Coach, we’ll run with it,’ ” Johnson said of Destelhorst and Ecker at a sweat-dripping news conference Thursday at a WSSC facility in Hyattsville.

Johnson said that repairs to the 54-inch main would be completed Thursday evening and that the main should be back in service by the weekend, after water-quality tests. Once the pipe is back up, mandatory water restrictions — no outdoor watering, limited household use — will be lifted in the affected area.

The utility chief continued to face questions about why WSSC officials hadn’t disclosed that valve-repair efforts were underway as they continued to warn the public to prepare for five days without water during a heat wave.

WSSC officials said on Monday evening that making repairs to the damaged main would require the unusually extensive and lengthy water outage because there was no way to redirect water around it.

The WSSC’s advisory caused businesses to close, hotels to empty out and residents to fill bathtubs and scramble for bottled water.

Even after Destelhorst and Ecker began working Tuesday morning, Johnson said, he and other utility officials didn’t think the mechanics would pull it off. Telling the public that the team was at work on a possible fix, he said, might have caused people to cut back on conservation efforts needed to keep the beleaguered system running and to ignore warnings to stock up on water. Then if the deteriorating pipe had blown, he said, people would have been caught without water on hand.

“I emphasize that we had no assurance we were going to be successful” with the valve repair, Johnson told reporters.

Destelhorst and Ecker got to talking with colleagues about the stuck valve at work Tuesday morning.

“We said, ‘Let’s just give it one more shot,’ ” said Jimmy Bowen, a unit supervisor who has worked for 20 years at the WSSC.

As Destelhorst put it: “They said it was broken. I fix things.”

Old, broken valves are nothing new in the Maryland suburbs, where the WSSC provides water to 1.8 million people in Montgomery and Prince George’s counties. Some of the roughly 78,000 valves in the 5,600 miles of water lines probably date back to the utility’s beginnings in 1918, WSSC officials said.

Regular preventative maintenance went by the wayside for almost a decade before the WSSC resumed a valve “exercising” program two years ago, officials said.

Destelhorst, 37, said the valve’s gears were similar to what he worked on for 11 years as an auto mechanic. Ecker, 41, of Scaggsville, said he approached the stuck gears as someone who had grown up tinkering with cars with his father.

When they reached the site of the valve, beneath a manhole near the Capital Beltway’s Pennsylvania Avenue exit, their work was cut out for them. Bowen and Billy Dove, who has spent 29 years working on the WSSC system, supervised. The group of four first spent several hours pumping water out of the undergound vault, so they could see the valve.

Destelhorst, who has been with WSSC for six years, and Ecker, who has 21 years with the utility, each took turns working in the underground vault while the other pointed a flashlight into the dark hole from above.

Each man worked for hours alone in the underground room — described as 20 feet by 10 feet with a ceiling about 20 feet high, trying to ignore the dank air and the thigh-high water.

“If you turn around and see the bugs and everything, you might get paranoid,” Ecker said.

Together, the team ground down the gears, carved out new teeth and meshed them back together. Sometime Tuesday evening — Destelhorst said the mechanics had lost track of the time — they got the valve to turn.

Destelhorst said they didn’t celebrate, not even with a high-five. They just did their job, he said. And how did they withstand the pressure of knowing that if they had failed, more than 100,000 people would have lost a service as basic as running water?

“You understand the severity of the situation, but you’ve gotta stay cool,” Destelhorst said. “Usually when things fail around here, it’s pretty epic.”

Luz Lazo contributed to this report.