Ontario Landlord's Guide: Water Quality and Legionella Testing

Written By: Canadian Water Compliance | On

Legionella Compliance, Legionella Monitoring, Water Quality Testing, Water Safety Tips, cooling towers, commercial buildings

A Landlord's Guide to Residential Water Quality Testing in Ontario

As a landlord in Ontario, ensuring your tenants have access to safe, clean drinking water is not only a moral responsibility but also a legal requirement. Regular water quality testing is essential to identify and address any potential contaminants that could pose health risks. This comprehensive guide will walk you through the key aspects of residential water quality testing in Ontario, including water testing, Legionella testing, and other important considerations.

Water Sources in Ontario

In Ontario, drinking water comes from two main sources:

  1. Surface water, such as lakes and rivers. The majority of Ontarians, especially in urban areas, rely on municipally treated surface water.
  2. Groundwater, which is accessed through wells. Around 23% of Ontario's population, primarily in rural areas, depends on groundwater for their drinking water supply.

Common Water Contaminants

Some of the most common contaminants that can affect residential water quality in Ontario include:

  • Bacteria, such as E. coli and total coliforms, which can cause gastrointestinal illnesses
  • Nitrates from fertilizers or septic systems, which can be harmful to infants
  • Lead from old plumbing fixtures or service lines
  • Pesticides and other chemicals from agricultural runoff or industrial activities
  • Naturally occurring minerals like iron, manganese, and arsenic
  • Legionella bacteria, which can cause Legionnaires' disease, a severe form of pneumonia

Regulations and Guidelines

In Ontario, the Safe Drinking Water Act, 2002 and its associated regulations set out stringent standards for drinking water quality. The Ontario Drinking Water Quality Standards (O. Reg. 169/03) specify maximum acceptable concentrations for various contaminants.

Landlords who provide drinking water to their tenants from a private source, such as a well, are responsible for ensuring the water meets these standards. If the rental property is served by a municipal water system, the municipality is responsible for testing and treating the water supply.

Water Testing Requirements and Procedures

Landlords with properties on private wells should test their water for bacteria (E. coli and total coliforms) at least three times a year - in the spring, summer, and fall. Additional testing for nitrates, lead, and other contaminants may be recommended depending on local risk factors.

Water testing is free for private households through local public health units. Landlords can pick up sample bottles and drop off water samples at designated locations. The samples are then analyzed at public health laboratories.

If a water sample tests positive for bacteria or exceeds the maximum acceptable concentration for any other contaminant, landlords must take immediate action to address the issue, such as disinfecting the well, installing treatment systems, or providing an alternative water supply until the problem is resolved.

Legionella Testing

Legionella bacteria can grow in building water systems, such as cooling towers, hot tubs, and large plumbing systems. Landlords of multi-unit residential buildings should consider testing for Legionella as part of their water management program, especially if the building has a cooling tower or centralized hot water system.

Public Health Ontario offers Legionella testing services for environmental samples, such as swabs from potential sources of exposure. If Legionella is detected, landlords should work with public health officials and water treatment professionals to implement control measures and prevent the spread of the bacteria.

Additional Considerations

In addition to regular water quality testing, landlords should also:

  • Educate tenants about the importance of maintaining clean and safe drinking water
  • Promptly address any tenant concerns or complaints related to water quality
  • Keep accurate records of water testing results and any corrective actions taken
  • Stay informed about emerging water quality issues and new regulations


As a landlord in Ontario, proactively testing and maintaining the quality of your rental property's drinking water is crucial for protecting your tenants' health and complying with provincial regulations. By understanding the common contaminants, following testing guidelines, and promptly addressing any issues, you can ensure a safe and reliable water supply for your tenants.

For more information on residential water quality testing in Ontario, consult your local public health unit or visit the Ontario Ministry of the Environment, Conservation and Parks website. Remember, investing in regular water testing and Legionella testing is an investment in the health and well-being of your tenants and the long-term success of your rental properties.