New guidance from Health Canada urges multifamily landlords and condominium corporations to implement water management programs to guard against microbial growth and chemical contaminant leaching in the plumbing systems of buildings with centralized hot water supply. That’s part of a proposed package of best practices for identifying, managing and monitoring water quality risks that can arise from operational or maintenance conditions in residential buildings.
Policymakers aligned with the federal-provincial-territorial committee on drinking water (CDC) have targeted microorganisms that can grow and persist in plumbing systems, and trace metals that can seep into potable water as it is stored and circulated within buildings. Factors such as temperature, flow rates, demand levels, piping diameter and configurations and the age of system components all contribute to the quality of water making its way to residential units.
Metals and inorganic substances may arrive via the municipal drinking water distribution system (DWDS) or from the materials that comprise a building’s water tank, pipes and fittings. Microbial contaminants that are naturally present in the environment can amass and proliferate within biofilms that are deemed to be “ubiquitous” in residential plumbing piping. Problematic strains such as Legionella, Mycobacterium and Pseudomonas are characterized as “opportunistic pathogens” that typically don’t pose a threat to healthy individuals but can present serious risks for those vulnerable to illness.
A draft guidance document currently posted on the Canadian government’s website for public consultation includes advice for drinking water suppliers, owners/managers of multifamily buildings, homeowners and occupants of single-family and low-rise housing, and anyone who consumes or is exposed to the water that flows from residential faucets, aerators, hoses and showerheads. Multifamily landlords and condo corporations are responsible for monitoring and addressing risks related to water distribution, storage and circulation from the point at which municipal supply enters into their properties.
“Complete eradication of OPPPs (opportunistic premise plumbing pathogens) is impossible, particularly in complex building plumbing systems where recolonization often occurs. However, steps can be taken to limit growth of OPPPs in plumbing systems to reduce the risks of human exposure,” the guidance states.
Infectious outbreaks are typically attributed to a chain of circumstances rather than any one factor, and vigilant risk management practices can interrupt that progression at various points. Health Canada references a series of related ASHRAE standards that contain risk management protocols for physical, chemical and microbial hazards in building water systems and specific applications for Legionella control.
Of these, ASHRAE standard 514 sets out parameters for devising a water management program (WMP) — a site-specific, multi-step exercise based on hazard analysis critical control points (HACCP) to identify types, infiltration paths and allowable thresholds of potential hazards, then apply required controls along with monitoring, documentation and verification processes. The guidance endorses that approach, but acknowledges that building owners/managers will need trained in-house expertise or third-party consultants to introduce and oversee such programs.
“For large multi-dwelling residential buildings, there is strong consensus that the development and implementation of a building WMP, also called a water safety plan for buildings, is a best practice to help building owners and managers oversee water quality in their buildings,” it states. “Important challenges with implementing WMPs are the demands for time and financial resources.”
Operational and maintenance measures
At a less technical level, the guidance describes the general features of a good plumbing system and suggests operational measures to reduce potential risk exposure. Owners/managers are advised to be particularly vigilant about biofilm and sediment that can nurture microbial growth and the presence of plumbing system components that contain lead. Optimum water temperatures, routine system flushing and communication to building occupants about risk-reducing procedures within their dwelling units should be ingrained in the strategy.
Cold water should be delivered at a temperature below 20 degrees Celsius (70⁰ F); hot water should be above 60⁰ C (150⁰ F) at its source and maintained above 49⁰ C (128⁰ F) as it travels through the pipes. Owners/managers should also ensure that pipes are properly insulated to avoid heat loss or gains that could compromise those temperatures, paying particular attention to piping in unheated mechanical rooms, near hot equipment or exhaust outlets and/or on outside walls.
The potency of water’s disinfectant agents diminishes as it travels away from the treatment plant and toward a building’s intake, and that process continues over the period that it might sit within the plumbing pipes. As well, there is more opportunity for microbes adhered to the inner surface of those pipes to infiltrate the water supply the longer it idles.
The guidance outlines flushing protocol for routine maintenance or more intensive remedial action. Operators should first open the cold water and let it run until freshly delivered-to-the-building water arrives; next, open the hot water and let it run until the temperature stabilizes around 50⁰ C (130⁰ F); then, finally, run the cold water again for approximately 10 seconds. This is a recommended weekly procedure at any outlet that has not been used in the previous seven-day period, and should begin with the outlet nearest to building’s intake point and move outward from there.
Flushing is also a short-term mitigation for reducing lead concentration in cold water, but the guidance warns that levels can rise again within 30 to 60 minutes. Replacement of lead-containing plumbing system components is the durable solution.
Other recommended maintenance activities include regular draining and flushing of hot water tanks (a task that may require a licensed plumber) and regular cleaning of showerheads, faucets and aerators to remove biofilm. If manufacturers’ instructions for cleaning the latter items are not available, the guidance cites a procedure considered suitable for Legionella control, which involves: washing in soap and water; descaling, if necessary, in white vinegar or a descaling solution for 30 to 60 minutes; rinsing and soaking in a 50 ppm bleach solution, equivalent to 1 teaspoon of bleach per 4.5 litres of water, for at least 30 minutes; rinsing and reassembling.
“In general, features of a good plumbing system design include: having good flow to all parts of the system (for example, minimizing stagnation, avoiding dead ends); avoiding materials that encourage growth of microorganisms or that can be sources of lead; minimizing heat transfer to and from hot and cold water supplies; and ensuring access for cleaning and maintenance of components,” the guidance observes. “Any measures to improve energy efficiency or reduce water usage should be assessed at the design stage to ensure that the control of OPPPs and inorganic contaminants is not compromised.”
Concerns about water-efficiency centre on lower flow rates, which can affect the transport of microorganisms and other contaminants and/or add to water volumes idling in the pipes and associated biofilm formation. Meanwhile, the guidance warns that climate change may create conditions that will make opportunistic pathogens more abundant or more resilient within plumbing systems since there are likely to be additional challenges to keep water temperatures below threshold for growth at around 25⁰ C.
Health Canada is accepting comments on the proposed guidance until Nov. 24, 2026.
