What does it mean when a school fails a lead test?

Hundreds of Ontario schools have failed lead tests in the past two years, including several within the Thames Valley District School Board. But school board representatives say their water is safe.

Many schools in the London area have been shown to have lead in drinking water

Lead from old pipes and fixtures can be leached into water sources, and is more common in schools built before 1990. (Lauren Mccllough/CBC)

How concerned should we be about lead in our schools' drinking water?

Hundreds of Ontario schools and daycares have failed lead tests within the last two years, including several facilities within the Thames Valley District School Board (TVDSB). 

These test results are available for download online

This means that at some point in the past two years, these schools have found more than 10 parts lead per billion in their drinking water. Ten parts per billion is the drinking water quality standard in Ontario, although any level of lead exposure is considered harmful.

Young children are particularly vulnerable to lead exposure, according to the World Health Organization (WHO), as it can interfere with their brain and nervous system development. 

The three schools within the TVDSB that tested highest for lead were: 

  • Huron Park Secondary School: Tested at 2500 parts per billion on August 11, 2016
  • New Sarum Public School: Tested at 250 parts per billion on July 18, 2016 and 190 parts per billion on July 22, 2016
  • Blossom Park Education Centre: Tested at 110 parts per billion and 78 parts per billion on August 17, 2016

But school board representatives say these numbers don't tell the whole story.

Later retesting at each of these schools showed flushed water samples with lead levels within acceptable limits. 

"Our drinking water is safe," said Jim McKenzie, superintendent of facilities services and planning with the TVDSB.

In all three incidents, the adverse taps were taken out and replaced, according to the school board's records.

How Ontario schools test for lead

The Thames Valley Education Centre main offices on Dundas St.
The Thames Valley District School Board maintains that their schools' drinking water is safe. (Dave Chidley/CBC)

All Ontario schools and daycares are required to test for lead in drinking water at least once a year. It is the only province that has this requirement, according to Gary Wheeler, a spokesperson for the Ministry of Environment and Climate Change. 

During the testing process, schools have to take a "standing" water sample and a "flushed" water sample. A standing sample refers to the first water to come out of the tap, whereas a flushed sample has been left to flow for a few minutes.

This distinction is important because flushing taps can reduce lead levels in drinking water.

If a tap gives standing and flushed samples within acceptable limits, they're still required to flush their pipes out once a week as a precaution. 

If either sample comes back higher than 10 parts per billion, then the school is required to flush their pipes daily.

Custodians do this before a school opens for the day, usually before 6:30 a.m, said John Neville, manager of facilities services for the board.

"It's their first priority in the morning," he said.

If a flushed water sample continues to come back with high lead levels, the school is required to take the tap out of service until the problem is fixed. This usually means replacing a fixture or water line, he said. 

All schools within the Thames Valley District School Board keep lead test results in their front offices. This information is publicly accessible. 

A stop-gap solution?

Still, some wonder if the current system of lead testing and flushing goes far enough.

Although 10 parts per billion is considered an acceptable limit, there is no level of safe exposure to lead. Over time, lead accumulates in the body and can lead to problems with the blood, brain, digestive system, heart and kidneys, according to the WHO.

Ideally, all plumbing and fixtures containing lead would be replaced, said Clare Robinson, an associate professor of civil and environmental engineering at Western University.

She acknowledged that this process would be both expensive and time-consuming.

"Unfortunately for the lead issue, there's just really no quick fix," she said.


Paula Duhatschek


Paula Duhatschek is a reporter with CBC Calgary who previously worked for CBC News in Kitchener and in London, Ont. You can reach her at