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​Facility Managers: Maintaining water quality during low building occupancy scenarios

As businesses start to welcome employees back to buildings, it is important that facility operators understand the importance of flushing building plumbing systems that have not been used for a while. Reduced occupancy has led to a decrease in water use and could mean longer periods of water stagnation within the internal plumbing systems of buildings. Without proper use and flushing within buildings, there is the potential risk of reduced water quality which could lead to the growth of microbes that are potentially harmful to human health, like Legionella.

We recommend that facility managers follow protocols appropriate to their buildings' systems which may include shutting down, draining and cleaning mechanical equipment where possible by flushing plumbing piping. Recently Public Health Authorities shared some guidelines around practices facility managers should review.

The Government of Alberta Guidance Document

This document is intended for both building owners and maintenance staff to provide support on flushing activities prior to building re-entry.

Flushing guidance

Accredited testing labs

If you would like the water in your business or home tested, we recommend contacting an accredited CALA lab.

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Flushing references and guidelines

For additi​onal support and resources regarding building flushing and best practices visit our list of resources.

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Government of Alberta flushing guidance

The Government of Alberta has released a guidance document to support businesses and buildings during COVID-19 re-entry. This document is intended for both building and business operators who operate within buildings that have been affected by low or zero occupancy and have had reduced water flow during the COVID-19 pandemic.  

Flushing Guidance

Ensuring your building's drinking water quality

 Flushing a business or office building

When buildings are vacant for a period of time, reduced water usage can result in increased water stagnation within the internal plumbing system. The best way to make sure drinking water is safe after a period of prolonged vacancy or very low occupancy is to carry out proper maintenance and flushing procedures before re-occupancy.

Reduced quality may include: leaching of metals from internal plumbing, loss of disinfection residual and the growth of microbes potentially harmful to human health, such as Legionella

We can't provide specific flushing activities for a place of business, but we have a series of recommendations and guidelines to help make sure the water within your internal plumbing is safe. 


We recommend following industry practices for recommissioning low occupancy buildings. Including:

  • Following manufacturer's guidance for both shutdown and start-up of equipment.
  • Test the water at the furthest tap from the municipal water service line for chlorine residuals.  
  • When testing for chlorine residuals, aim for at least 0.2 mg/L in your building's water system.
  • Performing maintenance on any filters and point-of-use devices according to the manufacturers recommendations. This could mean cleaning and replacing cartridges.
  • Flushing all water-use appliances such as: ice machines, dishwashers, showers, sinks, and toilets.
  • Cleaning showerheads, faucets and other fixtures that can produce steam.


Legionella is a bacterium that can grow in building water systems during periods of water stagnation or low flow. Legionella can cause Legionnaires' disease, a severe form of pneumonia, and lung inflammation.

For buildings that have been vacant or have seen a reduced occupancy and a decrease in water use there is an increased risk of Legionella growth within the internal plumbing system. Stagnant water can  cause a loss of chorine which can produce an environment in which Legionella thrives.  Legionella tends to grow in warm (25 – 42 C) stagnant environments where there is no disinfectant. It can also grow and proliferate in biofilms on the inside surfaces of plumbing piping and components. 

Ensure that your water system is safe to use after a prolonged shutdown to minimize the risk of Legionnaires' disease and other diseases associated with water.

If you suspect Legionella in your building's water system we recommend consulting the Centre for Disease Control detailing the process and procedures for removing Legionella. EPCOR also recommends contacting a certified testing lab to test your facilities water system. ​

  Flushing references and guidelines

We work closely with Alberta Health and Alberta Health Services to provide important information related to flushing protocols and practices. It's important to note that we cannot provide specific flushing activities at your place of business, but can recommend general flushing practices and important information regarding stagnant water in your home or business.

More information on flushing:

Government of Canada Building System Requirements
In response to COVID-19, the Government of Canada has released an important flushing guideline for businesses.

Environmental Science, Policy and Research Institute
Coronovirus Building Flushing Guidance

American Society of Heating, Refrigeration and Air Conditioning Engineers
Guidance to Minimize Legionellosis

U.S. Centres for Disease Control and Prevention (CDC)
Legionella Toolkit

Cross Connection Control Resources
American Water Works Association
Western Canada section on Cross Connection Control

American Water Works Association
Responding to Water Stagnation in Buildings with Reduced or No Water Use​


Cross Connection Control Program

Blackflow prevention is an important way businesses can minimize contamination risk. Our Cross Connection Control Program helps Edmonton's commercial and property owners ensure their backflow prevention is up to code and the water supply to your building is connected.
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