During the response to the COVID-19 pandemic, many buildings, such as office buildings, malls, educational institutions, hotels and motels, have been affected by low or zero occupancy and reduced water flow through the building. Under these conditions, water may stagnate, disinfection residuals decline and water temperatures change, creating environments which may support the growth and proliferation of disease-causing organisms including some types of Legionella and Pseudomonas.
Many components of the water system could be at risk of microbial growth including the water service delivery line, the building reservoirs, internal plumbing lines, as well as boilers and hot water lines with low water temperature. Disease-causing organisms, such as Legionella, can be transmitted through the aerosols generated at faucets, showers, toilets, humidifiers and spas as well as from ultrasonic mist machines, decorative fountains and cooling towers. (See the Reference section below for more information on Legionella).
Stagnation can also weaken and disrupt the protective scale on the piping and allow trace metals such as lead to leach into the water system. This may create sediment and discolouration in the water and further reduce the levels of chlorine.
Responding to the Risk
The Government of Alberta has developed a document to alert building owners and operators to the potential for microbial and chemical risks in water systems in buildings with limited or no occupancy, and to provide general steps on how to reduce those risks and prepare for building re-entry. Click Here to review the document.
In Alberta, the municipal drinking water delivered from the water mains has sufficient treatment (filtration and disinfection), levels of disinfectant, low temperatures and flow rates to suppress the growth of disease-causing organisms, and the capacity to inactivate the virus that causes COVID-19 disease. Municipal drinking water is considered safe.
If you operate or own a building with significant and prolonged reduced occupancy or no occupancy, take the steps outlined below that apply to your building to ensure that the potential risks from stagnant water are minimized. Depending on the complexity of the system, it may be helpful to consult with a plumber or building system engineer to determine the flushing procedures.
