When the city gets a complaint about a suspected leaky underground pipe, employees with the environmental services department pack up a van loaded with cutting-edge radar technology and head to the scene.

Every once in a while, however, their high-tech gadgetry lets them down and they resort to a pair of thin metal poles — divining rods.

The city says it still routinely uses the age-old detection technique, also known as dowsing or water witching.

"Definitely the other technology works more consistently," said Quentin Levesque, manager of what's known as the city's "locates group."

"Should they have difficulties or troubles using the other equipment, the divining rod is there as well."

Ottawa among last to use divining

The practice involves walking slowly over an area while holding one of the L-shaped rods in each hand. When the two rods cross, that's supposed to signify the diviner is standing over water.

Should they have difficulties or troubles using the other equipment, the divining rod is there as well. - Quentin Levesque, City of Ottawa

Traditionally it was used by farmers and other landowners to locate underground water sources so they'd know where to dig wells.

Ottawa is one of the last large Canadian cities to resort to divining, even occasionally.

These days the technique is "rarely used" by his crew, Levesque said, estimating they reach for the rods "once or twice" out of the 150 calls they receive in a typical week.

The staff of eight responds to calls from residents, contractors and construction companies who want to know what's underground before they start digging. They normally use electronic metal detectors or scanners, but will occasionally break out the rods.

No proof rods work

Despite the city's use, there's no scientific evidence that divining actually works.

"I'm not aware of any physical mechanism that would explain the response dowsers claim to receive," said Tom Al, a groundwater expert at the University of Ottawa.

"Whether it's electromagnetic, gravitational … it has to have a mechanism."

British biologist Sally Le Page recently called out large water companies in the U.K. for relying on divining, a technique she calls "magic" and compares to using a Ouija board. Like that spooky toy, Le Page said, divining rods really move because of the ideomotor effect — when your brain makes associations that subconsciously cause your muscles to move, seemingly on their own.

Al said he was surprised to learn the city still uses the technique.

While he can't speak to the lack of scientific evidence, Levesque said divining remains a widely accepted practice within the industry.

"I think it's a tool that's been available to the locates industry for many, many years."

Though there's no proof the rods can help sense water, Al said maintaining the practice probably can't hurt, either.

"If they use it and they think it works, maybe that's just fine. There's no harm to that."