February 22, 2005

Special report on state of Toronto’s underground plumbing

Watermain breaks: Location, location, location

By Peggy Hill

DCN Correspondent

A watermain breaks. A residential street floods as a consequence. It’s an inconvenience, even dramatic footage on the six o’clock news.

“But it’s not like all is hell breaking loose,” notes Dr. Balvant Rajani, senior research officer, Buried Utilities, with the Institute for Research in Construction (IRC), a branch of the National Research Council Canada (NRC) in Ottawa.

With 24 years experience, he is an expert in the behaviour, performance, analysis and design of municipal infrastructure.

“A watermain breaking in front of your house or my house is not a big deal. A watermain, to repair it, might cost anywhere from three to five thousand dollars. . . . The number of breaks economically that we can tolerate is very high in residential areas because the consequences are small.”

While trying to get people to put a watermain disruption in perspective, Rajani acknowledges that there are greater consequences, depending on the location of the break.

“A watermain breaking on Bay Street or near a hospital is very severe because if there’s not enough water, surgery can’t be performed, patient care can’t be delivered.”

A break under Bay Street in Toronto actually occurred last month, flooding an electrical transformer station. Power had to be shut off to the downtown area, leaving thousands of residents without heat. It happened on a weekend, so the inconvenience was not as severe.

"The number of breaks economically that we can tolerate is very high in residential areas because the consequences are small’

Dr. Balvant Rajani

On average, between 1,200 to 1,500 breaks occur each year in Toronto, which has 4,600 kilometres of watermain pipes. The number reached a peak in 1994, says Rajani, when there were over 2,000 breaks. It fell to 1,495 in 1999, 1,226 in 2002 and increased slightly to 1,354 in 2003.

Pipes in the suburbs are aging faster than downtown, says Mike Price, general manager of water and wastewater services for the City of Toronto. Pipes in the downtown area are made of iron, with a fairly thick wall. The thinner, ductile iron pipes installed in the suburbs in the 1950s, “especially with copper water services screwed into them,” are aging faster, he said.

Sam Morra, executive director of the Ontario Sewer and Watermain Construction Association, also noted the difficulty the city faces.

Sam Morra

“You’ve got a situation where you’ve got some really old pipes that are starting to break, and then some pipes that were put in after the Second World War that were thinner walled, ductile iron pipes, that are also breaking down, so it is sort of compounding the problem for them.”

While some old pipes are starting to break, “old doesn’t mean bad,” says Rajani. “If you think of Toronto, Toronto’s break rates, compared to other parts of the world are not bad, they’re quite good.”

He again noted that “everything is relative.” The city of Edmonton, which “is about one-quarter (the size) of Toronto” has a peak break rate above 1,500. “So you have to put everything in perspective. . . . Obviously Edmonton has a much colder climate.”

Edmonton and Calgary “had a very, very bad experience with ductile iron pipe,” so now they use PVC, he says.

“In Montreal, they just use ductile iron pipe, they don’t use PVC.” In Vancouver, ductile iron, and in Toronto “a bit of a mix.” The ductile iron pipe of today has a cement liner that protects it from internal corrosion from such things as chlorine.

What does not seem to have caught on in North America is polyethylene (PE), which is used mostly in Europe. The PE pipes are placed inside old pipes.

“We’ve looked at polyethylene,” says Price, “but we are using PVC. In terms of is there a written study that identifies all the pros and cons, there isn’t one, but there certainly has been lots of review work done.

“The general feeling is that at the moment, PVC will be the, shall we say, the leading material. We do use some ductile iron, albeit lined, in the downtown core where we have corrosive soils and stray electric currents. So, in general, we are moving to PVC, but it tends to be the smaller pipe sizes. We’ve had a couple of large main breaks, on 12- and 16-inch PVC, so we want to do some further study into the large diameter.”

Morra confirmed that the predominant material for smaller diameter watermain pipes in Ontario is PVC.

“I don’t know, to be honest,” why PE is not as popular here as in Europe. “We’re not here to advocate one type of material over another.”

PE’s use “in North America in new pipes is very low or none,” says Rajani. He suggested it might be partially due to culture, “and the level of comfort by the municipalities and utilities. People use what they are familiar with. If you buy coffee, for example, if you know Maxwell, you won’t buy Folgers.”

The city has also been protecting old pipes through a cathodic process. ‘Sacrificial’ anodes are placed in the pipe, which corrode instead of the actual watermains. It has worked “like a magic bullet,” says Rajani. “The breaks stop. Literally. But all this takes time,” he warns.

Editor’s note: Part 2 of this report — solutions, can the cycle of watermain pipes breaking be broken? — will run in tomorrow’s DCN.

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