The province tests well water for free. Samples can be dropped off at about two dozen locations across the city. (Jeff Semple/CBC)One out of every six private water wells tested in rural Ottawa last year was contaminated with harmful bacteria and unsafe for drinking, Ontario health inspectors report.

In addition, the 7,543 well-water samples tested in 2009 are believed to represent only about one quarter of all private wells in Ottawa, provincial and city health officials confirmed Wednesday. Most of the city's 28,000 rural homes rely on well water.

Karen Demont got her well tested when she bought her home in Metcalfe, a community in Ottawa's rural southeast, a few years ago. The results showed high levels of coliform, or E. coli bacteria, which can cause gastrointestinal illness and sometimes even death. The well was immediately cleaned, and she's had it re-tested regularly by the province ever since. She's surprised not everyone does.

"It's not that much work — run your water for two minutes, fill your container and drop it off," she said Wednesday.

There are about 28,000 rural homes in Ottawa. Most rely on well water, and about a quarter got their water tested last year. (Jeff Semple/CBC)Wells can become contaminated when water drains into the water table after running over fields spread with animal feces or other reservoirs of bacteria. They can be cleaned using a bleach mixture, following instructions provided by the Ontario government.

Ottawa Riverkeeper Meredith Brown, head of a local water conservation group, said contamination sources are usually beyond the control of nearby homeowners.

"As an individual well owner, you're responsible for monitoring your own drinking water and ensuring you're doing everything you can to protect that source water," she said.

Unlike some other municipalities in the province, the City of Ottawa has no system to monitor and track water quality in private wells.