Water Maintenance Program and Testing for Presence of Legionella

Updated: June 29, 2021

As a result of the pandemic, most U of T buildings have had limited use which has resulted in limited water flow. Stagnant water creates conditions for Legionella bacterial growth.  We have been and will continue to test for Legionella in the water, as part of the proactive and routine maintenance of our buildings.

The University began Legionella testing as part of its return to work re-entry procedures in the summer 2020 to ensure a safe working environment. The Water Maintenance Program involves flushing the water in our buildings and then measuring it for the presence of the Legionella bacteria.

The University’s Water Maintenance Program exceeds Ontario Public Health guidance for testing on buildings with reduced occupancy.  The remediation and testing methodologies set out in the University’s Water Maintenance Program are in line with the Ontario Public Health and Federal Public Works guidelines for Canadian government buildings. The Legionella action concentrations are also in line with the Canadian, American and international standards.

The Water Maintenance Program’s testing has found the presence of Legionella in some buildings. As soon as Legionella is detected in a building, remediation measures are immediately undertaken as detailed below. Remediation includes closing off areas as necessary and not reopening them until retesting indicates they can be reopened. We remediate any instances of the presence of Legionella immediately and retest to ensure our control measures are successful.

Legionella in cold water is not a material risk as legionella favours warm water, but in temperatures of 25-42°C it can multiply and pose a health risk if other concurrent conditions are also present (e.g. warm water with mist such as showers or spray heads on taps).  The presence of Legionella in the water is not a material risk to the general occupants unless it is aerosolized. Also, the individual is generally a member of the susceptible population to acquire Legionellosis as noted in Public Works and Government Services Canada, Control of Legionella in Mechanical Systems, the Public Health Ontario, Legionella: questions and answers, 2nd edition, Legionellosis: Key Considerations for Case and Environmental Exposure Investigation, and Center for Disease Control, Legionella (Legionnaires’ Disease). The development of the Water Maintenance Program was intended to address any concerns pertaining to our potable water system.

As per CDC, most healthy people exposed to Legionella do not get sick. People at increased risk of getting sick are:

  • People 50 years or older
  • Current or former smokers
  • People with a chronic lung disease (like chronic obstructive pulmonary disease or emphysema)
  • People with weak immune systems or who take drugs that weaken the immune system (like after a transplant operation or chemotherapy)
  • People with cancer
  • People with underlying illnesses such as diabetes, kidney failure, or liver failure


Table 1 – Water Testing – St. George Status Results (qPCR)

Table 2 – Water Testing – St. George – Historical Results (qPCR)

Table 3 – Water Testing – UTSC Results – November 10, 2023

Table 4 – Water Testing – UTM Results – January 24, 2024

Table 5 – Water Testing – UTM E. Coli and Total Coliform Results – January 24, 2024

Water Testing Schedule

Procedures for Isolated or Multiple Point Legionella Source Detection

Potable Water Maintenance Program – Legionella FAQs 

Potable Water Maintenance Program Communication Flow Chart

For the University’s Potable Water Maintenance Program, please click here.

We continue to encourage JHSCs to provide feedback. University community members are also welcome to review and comment here.