Municipalities in the Greater Toronto Area are taking new steps to stop water thieves from targeting fire hydrants.

The Region of Durham says 672,170 cubic metres of water — enough to fill about 270 Olympic-size swimming pools — was illegally pumped from its hydrants in 2016, forcing the region to absorb $60,000 in lost water fees.

The thefts can also cause hydrants to freeze in winter, which means firefighters can't use them in an emergency, the region says.

Since 2009, 29 companies in Durham have been convicted of water theft. So far in 2017, Durham has caught three thieves in the act, but the region suspects that many more go undetected.

Gone in 30 minutes

In nearby Markham, Ont., the city received just five reports of water theft in 2016, but it estimates that annual losses are closer to $30,000.

Most large water trucks can be filled in just 30 minutes, said Jim Cunningham, a supervisor in Durham's works department. And if no one spots the theft happening, the culprits are difficult to catch later, he said.

The companies that have been convicted of the theft in the past often use a lot of water in their line of work, Cunningham said. They've included hydro-seeding firms, car washing businesses, pool water suppliers and street sweepers.

In 2016, Whitchurch-Stouffville company Ontario Hydro-Vac pleaded guilty to water theft related to an incident in King Township.

Licensed users

In an attempt to preserve its water, the Markham fire department recently installed a lock on a hydrant that had been targeted by water thieves.

The Region of Durham has taken a different approach. It has placed indicators on several select fire hydrants from which licensed users can take water. The hydrants are carefully monitored.

The real danger of water theft comes not from lost revenue, but the tampering with fire hydrants, the affected municipalities say.

Street sweeping companies are among a wide range of culprits. (CBC)

After hydrants are illegally tapped, the normally dry vessels become filled with water, Cunningham said.

"So if we don't know that that hydrant has been used, come wintertime, the fire hydrant will freeze, which means that we cannot provide fire services from that hydrant if something happens."

In the past 10 years, Cunningham said there has been one instance when firefighters were unable to use a hydrant because it froze after being illegally used.

Water contamination

Water theft can also contaminate the drinking water supply, according to Durham, Markham and King Township. That can happen when the person tapping into a hydrant does not use a device to prevent backflow from the truck into the water system.

Following its 2016 water theft incident, King Township launched a public awareness campaign in an attempt to create a different type of neighbourhood watch.

In a sign of the campaign's success, several residents have called in suspected water thefts that turned out to have been authorized by the city, a spokesperson told CBC Toronto.

Durham also called on its residents to keep an eye out for water thieves in 2015. That led to charges when its workers were able to reach one location before the thief took off.