Image of water running into a sink.

If your workplace has been closed for some time or has had reduced occupancy, it is important to flush your water system before re-opening to employees and/or customers. Water that has been sitting in your pipes for extended periods can get stale and lead to the growth of microbes that are potentially harmful to human health. Ensure good water quality and safe drinking water by thoroughly flushing your building’s water system. 

While we cannot provide specific flushing procedures for each place of business, we have a series of general guidelines to help ensure the water in your building is safe.  

Parts of the water system that are most important to flush because they have the greatest opportunity to make people sick include: 

  • faucets used for drinking water or food preparation 

  • drinking fountains 

  • ice machines and refrigerators with ice makers 

  • showers 

  • kitchen sink sprayers 

  • HVAC systems 

  • water features that generate aerosols (fountains, ;humidifiers, spas, etc.)

  • parts of the water system that are used by children 

  • parts of the water system used by the elderly or those with underlying health conditions 

If you have issues with water quality after you have flushed your system you can call 780-467-7785.

General guidelines: 

  • Run your taps, cold water first then hot. 

Remove any aerators or point-of-entry treatment units before flushing.

Turn on all the taps and run the cold water until it feels cold and then the temperature remains steady. This may take some time depending on the size of your building. Make sure you flush water through every outlet to clear all the pipes.

Once the cold-water lines have been flushed then you can flush the hot water lines. You should also drain and refill he hot water tank. Ensure the hot water system is at least 50 degrees Celsius throughout.

  • Flush every toilet 

  • Flush everything else

Flush any other appliances or systems with a water connection such as refrigerator filters, drinking fountains, coffee makers, ice machines, etc. according to the manufacturer’s recommendations.

Clean aerators, showerheads, faucets and any other fixtures that can produce aerosols and/or steam that people could inhale.

Replace all point-of-use filters, including the filter in refrigerators. 

Large buildings: 

Large buildings require an initial flush to remove the low-quality water and contaminates that have been sitting in the pipes and then follow-up flushes to bring the building back up to acceptable water quality. In between the flushes all fixtures should be cleaned to remove contaminants from internal structures.

  • If your building has one, follow your Water Management Plan (WMP). A plumber or building system engineer can assist in the development of WMPs.  

  • Flushing should proceed in a single direction (unidirectionally) from the point where the water enters the property to the furthest point of the water system.

  • If your building has separate zones flush zone by zone, starting with the zone nearest the building supply and moving progressively outward from there. Identify the starting point of the zone and most distant faucet to ensure you are flushing it completely. In each zone flush the cold water system first and the hot water afterwards.

  • Large buildings may have a variety of places where water is stored. They should all be identified, drained, and flushed with clean water.

Water quality testing 

Following flushing, total chlorine residuals should be 0.2mg/L or greater. For assistance with chlorine and turbidity testing, you can make an appointment for a Utilities Operator to come to site by contacting 780 -467-7785. For testing beyond chlorine and turbidity, we recommend contacting an accredited Lab.

More information on flushing 

Government of Alberta: Flushing Water Systems

Environmental Science, Policy and Research Institute: Coronavirus Building Flushing Guidance

Water and wastewater services and 24-hour emergency
Phone: 780-467-7785
Fax: 780-464-0557

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Last updated: Friday, October 06, 2023
Page ID: 50769