Water commission officials say their monitoring system was not extensive enough to alert them to a water main break in Chevy Chase that caused headaches for Montgomery County commuters in mid-March.

Officials told a Montgomery County Council committee the break on the pipe, which burst on March 18 and left a 50-foot crater on Chevy Chase Lake Drive, was not detected because of a gap in how their equipment found and alerted them to breaks.

And, an inspector made a critical misjudgment after misdiagnosing the water main break for a leaky valve. Someone called Washington Suburban Sanitary Commission officials to complain of water flowing out of Chevy Chase Lake Drive at about 1 p.m., but after an inspector decided it was a leak and recommended crews come the next morning. Later than evening, at about 7:45 p.m., the water main exploded.

Officials said they are concerned that their technology was insufficient, and are studying the break to see what other preventative measures they can take.

"We assume there's something we need to be doing, but we're not sure exactly what," said Gary Gumm, chief engineer for the WSSC.

Councilman Roger Berliner, D-Bethesda, requested the utility meet with the county council after being flooded with communications by constituents complaining of the break that delayed traffic and put parts of the county on water restrictions.

Gumm told the committee that particular piece of pipe is designed similarly to a small number of pipes within the utility's network. He said officials are unsure why the pipe burst.

There is a sensor on the pipe used to identify possible problems before they break. Gumm said that didn't go off because the sensor uses the acoustic sound of wires breaking -- which typically occurs when water mains break -- but where the Chevy Chase pipe broke, there were no wires.

"We did not know that this type of pipe might fail without wires breaking first," said Gumm.

Council members said they were concerned with the frequency pipes are breaking in Montgomery County, and the proximity of those breaks near homes. The Chevy Chase break caused water to shoot up 40 feet in the air. Berliner questioned what these aggressive water main breaks could mean for the safety of those that live and work near them.