Potable Water Maintenance Program – Legionella FAQs

Updated: June 29, 2021

1. Legionella

Legionella is a waterborne pathogen causing Legionnaires’ disease. Legionnaires’ disease is an illness characterized by pneumonia, caused by infection with Legionella species such as Legionella pneumophila. Another name for Legionnaires’ disease is legionellosis. For more information, please see Public Works and Government Services Canada, MD 15161 – 2013, Control of Legionella in Mechanical Systems.
Legionella bacteria are widespread within the natural water environment (rivers, lakes, ponds, and reservoirs) and can be found in soils and mud. It can also be found within biofilm growing inside a building’s plumbing and given a suitable conditions, it can form biofilm from which the bacteria may be released from taps, showerheads and other points of discharge. For more information, please see Public Health Ontario, Legionella: questions and answers, 2nd edition.
There are a number of important factors that provide an environmental for Legionella to multiply: water temperature, the presence of biofilm, water stagnation and the type of plumbing material and components present. For more information, please see Public Health Ontario, Legionella: questions and answers, 2nd edition.

Water Temperature The water temperature required for optimal Legionella growth is between 25°C and 45°C.
 
Biofilm Biofilms are slimes that form on surfaces in contact with water, such as the inside walls of water pipes, air conditioners, cooling towers, whirlpools, showerheads, taps and humidifiers.

Water stagnation or low flow During period of water stagnation or low flow, hot water temperature decreases and cold water temperature increases. Also, a decrease in residual disinfectant levels can occur. Both of these factors are favourable to the development of biofilm and can produce an environment in which Legionella amplifies. Facilities that have undergone extensive renovations over time may have redundant pipework/dead legs in which water can stagnate. Infrequently used fixtures can also allow water to stagnate.

Other factors
    1. Inadequate disinfection in the building’s water systems can lead to the proliferation of Legionella.
    2. Certain plumbing materials can favour biofilm colonization in potable water systems.


  The University’s Water Maintenance Program was developed to address these factors. The 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.
Research has shown plastic and rubber materials found in plumbing components, such as flexible hoses or thermostatic mixing valves, are susceptible to such colonization. For more information, please see Public Health Ontario, Legionella: questions and answers, 2nd edition.

2. Legionella Exposure

Legionnaires’ disease is principally acquired by inhaling minute aerosolized droplets of contaminated water or aspiration of fluid from the mouth or stomach into the lungs. It is not considered to be transmitted from person to person or from ingestion unless aspiration occurs. The mere presence of Legionella bacterial in a building’s water system is not sufficient to cause Legionnaires’ disease. Certain factors that increase the risk of someone acquiring Legionnaires’ disease include:
  • Conditions suitable for growth of the organisms such as stagnation, suitable water temperature (25°C - 45°C) and deposits that are a source of nutrients for the organisms.
  • A means of creating and spreading inhalable droplets such as showers or spray heads on taps.
  • Exposure of vulnerable persons (e.g., elderly, dialysis patients, smokers, newborn infants, persons with underlying medical conditions, or persons taking medications that weaken to immune system) to colonized water that in inhaled or aspirated into the lungs.
  • For more information, please see Public Health Ontario, Legionella: questions and answers, 2nd edition.
    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). 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
  • The University follows applicable public health guidance. We appreciate that persons may have specific medical considerations. Our procedures as per the Potable Water Maintenance Program adhere to and/or exceed the requirements of Ontario Public Health in terms of when testing needs to be performed (e.g., Ontario Public Health does not set a threshold for testing water systems after a certain length of a building being unused or having low occupancy, the University has developed and applied a threshold based on Public Works and Government Services Canada, MD 15161-2013, Control of Legionella in Mechanical Systems document in order to adopt a systematic approach to controlling legionella on our campus).

    If you would like more information on legionella, please refer to:
    1. Public Works and Government Services Canada, MD 15161-2013, Control of Legionella in Mechanical Systems, Page 48, under “3. Inhalation”.
    2. Public Health Ontario, Legionella: questions and answers, 2nd edition, Page 23, question 19.
    3. Public Health Ontario, Legionellosis: Key Considerations for Case and Environmental Exposure Investigation, Slide 15.
    4. Centers for Disease Control and Prevention, Causes, How it Spreads, and People at Increased Risk.
    We also appreciate that individuals may also have specific questions regarding legionella and their particular medical condition and they are welcome to contact our Occupational Health Nurse at ehs.occhealth@utoronto.ca.

    3. Potable Water Maintenance Program

    The purpose of each of the maintenance procedures described in the University of Toronto Potable Water Maintenance Program is to confirm the system is function effectively, which means the following:
  • Potable water is distributed to the point of use in a manner ensuring safety of the user.
  • Contaminants in the water are controlled to concentration below the standards set in the Ontario and Health Canada Drinking Water Guidelines include lead and Legionella.
  • The Maintenance Protocol is specific to the University of Toronto potable hot and cold water only.
    Under the Potable Water Maintenance Program, the Predictive Maintenance Procedure (page 4) uses a risk-based predictive approach to systematically ensure the minimization of Legionella bacteria in the campus potable water systems operationally ongoing. This is based on the trended presence of Legionella identified by prior predictive investigations and risk environments. This approach is also used to prioritize re-entry maintenance after a prolonged shutdown or low-flow situation that exceeds four weeks.

    The Potable Water Maintenance Program further explains how building risk levels are categorized using low, medium, and high as benchmarks on page 5.
    Generally, all taps are opened and flushed however, flushing for each building is dependent on the size of the building. For building specific information, please contact ehs.office@utoronto.ca.
    Yes, there is a flushing procedure.

    Step 1 – Identify all risk locations as described that have not been used in the last four weeks (PPE requirements identified in the Potable Water Management Program).

    Step 2 – Remove all components from the fixtures that create the risk.
    a. Shower Heads
    b. Faucet Aerators
    Place the removed components in solution containing 2.25% sodium hypochlorite solution during the Step 3 activities to remove any contaminants.

    Step 3 – Commence flushing depending on specific facilities as follows:
    a. Sinks or Hand/Face wash Facilities/Food Preparation Areas*

    1. Cold Water
    Flush cold water until the water is clear, and once clear, for a further 10 minutes. If water becomes turbid (discoloured) during flushing, continue flushing until it becomes clear again, and for a further 10 minutes once clear. To minimize splashing place a cloth or shroud over the faucet enabling the water to drop to the drain contained in the shroud.


    2. Hot Water
    After cold water flush, flush hot water at 50°C (122°F) for 15 minutes. If the water becomes turbid, flush until water becomes clear, and for a further 15 minutes once clear. To minimize splashing place a cloth or shroud over the faucet enabling the water to drop to the drain contained in the shroud.

    *Food preparation areas as described above to be flushed using the same methodology as ‘Sinks or Hand / Face Wash Facilities”. Any equipment left undrained during last 4 weeks must be drained then cleaned in accordance with the original manufacturer’s instructions.

    b. Showers and Bathing Areas:
    1. Remove the showerhead and the faucet aerator, then place them in a 2.25% sodium hypochlorite solution. Affix a hose over the shower pipe to empty directly to the floor drain. Place a towel over the hose at the floor drain to eliminate possibility of spray or splash back. Flush the faucet at the same time as the shower; ensure splashing is minimized by using a shroud.

    Cold Water
    2. Flush cold water until the water is clear, and once clear, for a further 10 minutes. If water becomes turbid (discoloured) during flushing, continue flushing until it becomes clear again, and for a further 10 minutes once clear. To minimize splashing place a cloth or shroud over the faucet enabling the water to drop to the drain contained in the shroud.

    Hot Water
    1. After cold water flush, flush hot water at 50°C (122°F) for 15 minutes. If the water becomes turbid, flush until water becomes clear, and for a further 15 minutes once clear. To minimize splashing place a cloth or shroud over the faucet enabling the water to drop to the drain contained in the shroud.
    2. Remove towel and or shroud and place it in the bleach solution. Remove hose and place it in the bleach solution to remove possible contaminants.
    3. Replace the showerhead and aerator; turn on water to ensure it is not leaking.

    c. Toilets and urinals:
    1. The toilets and urinals operate using cold water provided by the City of Toronto at approximately 8°C (46°F). Legionella is considered a low risk in water colder than 20°C (75°F). If the facilities have not been used or cleaned in the past four weeks, the facilities to be flushed twice to remove line debris.

    d. Drinking Fountains:
    1. Drinking fountains are operated using cold water, less than 20°C (75°F), and therefore legionella is considered a low risk. Fountains should be flushed for 10 minutes to clear the system including any accumulated debris that might exist.

    4. Testing for the Presence of Legionella

    Yes, 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 may include 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 as soon as possible and retest to ensure our control measures are successful.

    For more information on remedial actions, please review the University of Toronto’s Potable Water Maintenance Program.
    Results for buildings can be found on the EHS webpage, Water Maintenance Program and Testing for Presence of Legionella updated once a week and the report is sent to the co-chairs. Any interim results are also provided to the JHSC co-chairs.
    A Water Testing Schedule was created to keep occupants updated on which buildings are tested when. We encourage occupants to check the schedule regularly for the most up-to-date information on testing in their building. Due to the duration and complexity of flushing a system and the required waiting time, there may be situations where re-testing is scheduled only a day or two in advance.
    Water sources are currently being tested at randomly selected sources with an attempt to cover a range of both source types and floors. If Legionella is found on this initial screen, the source selection is expanded when retesting is conducted. It is not necessary to test every single shower, faucet and pipe but rather to focus on areas where there is an increased potential for legionella to grow. These showers are part of the distribution loop which gets tested for functionality once a year and are not tested for legionella at this time. The lab water supply is typically separate from the drinking water supply to the rest of the building.

    Following the initial screening phase, buildings selected for legionella testing will be based on risk categorization, as outlined in the Water Maintenance Program (pages 4-5). The Water Maintenance Program is based on established government practices.

    In addition to testing for legionella, temperature checks are regularly conducted. Temperature checks are conducted to verify that water is stored and distributed at temperatures that reduce legionella risk. As per the Water Maintenance Program, on page 4, hot water storage is verified at 60°C, in the distribution system at 50°C, and the point of use at 43°C. The point of use testing is at the end of the distribution system as part of the preventative maintenance tasks.
    It is not necessary to test every single shower, faucet and pipe but rather to focus on areas where there is an increased potential for legionella to grow. We do test more locations on a follow-up visit as required. After the tested locations are all green, the predictive/preventive maintenance plan comes into effect.
    There are three benchmarking categories:
  • Green: <10 GU/mL or CFU/mL*
  • Orange: 11 to 100 GU/mL or CFU/mL
  • Red: >100 GU/mL or CFU/mL


  • *GU=Genomic Units from qPCR; CFU=Colony Forming Units from Cell Culture
    We take precautions whenever we find a detectable amount of legionella. For example, there are some buildings that are all green, but Legionella detected (< 10 GU), we still continue with flushing and retesting until Legionella is not detected.

    In addition, in practice the preventive/predictive maintenance approach will include results of testing as a risk factor. Buildings that are found to have tested positive for any presence of Legionella will be tested more frequently.
    Orange results indicates that normal operations can continue however, flushing of the system is needed along with re-testing. For clarity, in the orange category, occupants can continue using the facilities.
    Notice to general occupants are sent by F&S for any orange or red test results. Results are communicated to the JHSC as well as posted on the EHS webpage on Water Maintenance Program and Testing for Legionella. To subscribe to F&S Service Alerts please click here.
    Red results indicate flushing of the system along with shutdown of the affected areas and re-testing. Remediation may require additional maintenance e.g. replacing mixing valve, temporary increasing water temperature above operating values. The affected area is closed off and inaccessible to occupants. Occupants can continue to use other facilities within the building.

    Notice to general occupants are sent by F&S for any orange or red test results. Results are communicated to the JHSC as well as posted on the EHS webpage on Water Maintenance Program and Testing for Legionella. To subscribe to F&S Service Alerts please click here.
    The qPCR technology measures DNA in samples and gives results in genomic units per millilitre (GU/ml), a measure that is intended to be equivalent to plate counts. Thus, a reading of 18 would be a positive detection of Legionella DNA but would not be a precise measurement of the number of living bacteria. A positive result does not indicate that Legionella is viable and growing, rather it indicates that DNA from live or dead Legionella has been detected. As a result, monitoring over time is needed to determine if levels are climbing, descending, or remaining static.
    Although there are instances where qPCR may provide a false positive result, the focus is to eliminate all traces of Legionella in the system whether it is considered alive or dead as a positive result indicates the Legionella may regrow.
    Eyewashes are flushed weekly by the lab occupants.

    Eyewashes use cold or tepid water. Tepid water is a mix of hot and cold water that is regulated by a mixing valve. Tepid eyewashes tend to be found in labs that have been renovated more recently. Cold water eyewashes tend to be in older labs. Testing for legionella overall in buildings occurs in the hot water system as this is where Legionella thrives so testing of eyewashes is focused on tepid systems.

    Cold Water Only Eyewashes
    Legionella does not like chlorinated water, which is the water supplied to cold water only eyewashes. By flushing eyewash stations frequently with chlorinated water, stagnant water in the dead leg is cleared, and the risk of legionella growth is minimized. The lower water temperature and the normal operations of flushing minimize the risk of legionella growth.

    Tepid Eyewashes
    Tepid eyewashes will be tested in buildings where there has been legionella found in the laboratory plumbing supply.
    For red results, the eyewash station would be closed for remediation and undergo cycles of hot water flushing and re-testing until there is a green result. Interim measures would need to be implemented e.g. a portable eyewash/squeeze bottle for use in the event of an emergency. Interim measures will be reviewed and assessed on a case by case basis by EHS. Please contact geoff.shirtliff.hinds@utoronto.ca for a risk assessment.

    For orange results, normal operations can continue in the lab, the eyewash is hot water flushed, along with re-testing. For clarity, in the orange category, occupants can continue using the facilities. For more information, please refer to the University’s Water Maintenance Program (Potable water).

    5. Building Maintenance

    The domestic water system is separated from the HVAC system. For the HVAC system, there is a chemical used to treat the water to prevent Legionella growth and the concentration of the chemical is monitored in the system at all times.
    EHS is monitoring the situation closely and once testing is completed in a building, the building moves on to the Predictive/Preventative Maintenance Procedure under the University’s Potable Water Maintenance Program.

     

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