WSSC crews work to repair a broken water main at Connecticut Avenue and Chevy Chase Lake Drive in Md. Pepco crews also work to repair power lines that came down when a tree pummeled by the geyser fell about 5 am.  (Katherine Shaver/The Washington Post)

A major water main that exploded in Chevy Chase on Monday night and led to ongoing water restrictions for 1.8 million people in Montgomery and Prince George’s counties had equipment designed to alert the utility of an impending break, a utility official said.

But the Washington Suburban Sanitary Commission did not receive any warning of the massive break, which disrupted Tuesday’s morning and evening commutes in Montgomery.

The acoustic sensor was installed in 2010 after an inspection of the pipe, which is five feet in diameter and lies under the eastern edge of Connecticut Avenue at Chevy Chase Lake Drive, according to the WSSC. The equipment is designed to detect the “ping” sounds that emanate from a concrete pipe as its reinforcing steel wire begins to snap, giving the utility time to shut down a pipe before it ruptures.

WSSC officials said they don’t know whether the sensor failed or the break was caused by something other than weakening wires. A problem in a steel joint, where there are no reinforcing wires, would not be detected by the sensor, WSSC officials said. A pipe also can break suddenly if its supporting bed of soil beneath it erodes.

The equipment is part of a break-detection system that the WSSC has spent $21.2 million on since 2007 to warn of weaknesses in its largest aging underground water mains, which are considered particularly dangerous because they are highly pressurized and can explode without warning. The break in the 33-year-old Chevy Chase pipe, which occurred about 8 p.m. Monday, sent a geyser of water four to five stories into the air and blasted through asphalt on Chevy Chase Lake Drive, leaving a 20-foot-deep crater.

What happens when water mains burst

WSSC spokesman Jim Neustadt said it will take several months for a forensic investigation to determine the exact cause of the break. He said it occurred in an area where the 60-inch main joins a 54-inch pipe, but he said he didn’t know whether that would prove significant.

“Nothing is perfect,” Neustadt said of the break-detection equipment. “You take the best technology and the best knowledge you have, and you put it to use in the best way you can.”

He said that it was the first time a WSSC pipe with the break-detection system had burst but that the WSSC has known that no technology is “fail-safe.”

Across the country, local officials are struggling to maintain and replace aging water and sewer systems.

Another break, of an eight-inch water main in Bethesda, on Tuesday morning closed River Road between Bradley Boulevard and Persimmon Tree Road for much of the day, snarling traffic.

Travis Wagner, a vice president for Pure Technologies, the Columbia company that is installing and monitoring the acoustic equipment for the WSSC, said Tuesday afternoon that he hadn’t been able to inspect the Chevy Chase pipe or his company’s equipment. Wagner said the company has installed the equipment in 560 miles of pipe worldwide since 2005 and has never failed to detect a weakening main in time for a utility to intervene.

“We’ve never had an issue detecting a wire-break-related failure,” Wagner said. “I know WSSC’s goal is to find out [the cause of the break] as soon as possible. There are a lot of questions.”

Jerry Irvine, a spokesman for the Washington Suburban Sanitary Commission, explains how a 54-inch, highly pressurized water main burst along Connecticut Avenue in Chevy Chase Lake, just inside the Capital Beltway, late Monday night. No one was injured, and the break caused no significant property damage, but it blew a large crater in part of Chevy Chase Lake Drive, where part of the road and sidewalk were ripped out. The pipe was installed in 1980 (Katherine Shaver/The Washington Post)

WSSC crews, using a keylike device on a 16-foot pole, cut off the geyser about 3 a.m., which required turning two valves 150 times to isolate the broken section and redirect water around it.

Connecticut Avenue, a major commuter artery between the Maryland suburbs and downtown Washington, remained closed overnight until 7 a.m., when the southbound lanes reopened. One northbound lane reopened Tuesday afternoon, but rush-hour backups continued.

WSSC officials said drinking water remained safe but ordered people in Montgomery and Prince George’s to conserve it by limiting toilet flushing and postponing laundry to help restore the system and maintain water pressure for fire hydrants and hospitals. Violators could be fined up to $500. The system lost more than 60 million gallons during the break, the WSSC said.

No one was hurt and no private property was damaged, WSSC officials said.

Even so, it was the kind of unforeseen rupture that officials in Montgomery and Prince George’s say WSSC assured them would be prevented with investments in a sophisticated break-detection system.

Those counties’ officials have cited it as a reason they have been skeptical that WSSC’s proposal to limit new building within 80 feet of its largest mains is necessary. The county officials have said expanding the building setback from the current 25 feet to 80 feet would prohibit the kind of dense, urban development the counties are planning on to attract and focus economic growth.

County Council member Roger Berliner (D-Potomac-Bethesda), who has questioned the need for a larger building setback, said he wants to know whether the technology is reliable. Berliner’s district includes the site of the Chevy Chase break as well as that of a major break in 2008 along River Road in Bethesda, where motorists had to be rescued from a torrent of water.

“If it did have this equipment that our communities are relying on, then we really need to understand what went wrong,” Berliner said. “I’m sort of tired of these unnatural disasters, and I know my community is. . . . We need to understand exactly what went wrong here in order to judge fairly what we need to do going forward.”

The break-detection equipment led the WSSC to shut off an eight-foot pipe in Montgomery in 2010 after a flurry of “pings” was detected.

WSSC officials have said that about 80 miles of its pipe four feet in diameter and larger will have the equipment installed by this summer.