Re-opening Buildings and Your Water System

May 8, 2020
Public Works
Water Infrastructure Maintenance

The following ONLY applies if no one has been using the water in a building for at least 3 to 4 days

What You Need To Know
When buildings are closed or are on low occupancy for any prolonged period, water in the building becomes stagnant and can pose serious health risks.  Harmful microbiological and chemical contaminants can grow or leach into the water supply. 

The effect of such stagnation will vary between each building based on factors such as length of the shutdown, size of the building, number of occupants, complexity of the system, integrity of the plumbing, and maintenance performed during the shutdown.

While municipal utilities are responsible to get clean, safe drinking water to each property, it is the responsibility of each property owner to ensure they maintain the safety of that water within their building.  

How Does This Happen
When a building is not in use and its water system is not actively maintained, the water becomes stagnant within the pipes, equipment, and any storage tanks.  The disinfectant residual decays and disappears, hot water systems can become cooler and cold water systems can become warm.   This can lead to the growth of bacteria, lead and copper leaching and the accumulation of harmful disinfection by-products. 

Since many facilities have shut their doors over the last few weeks and have been mostly vacant, we are reminding you to get your water running! 

We are encouraging residents and business owners to follow the guidelines provided in the checklist only if no one has been using the water for at least 3 to 4 days. What this does is flush your internal plumbing system, as the water has sat in your pipes for longer than normal. Similar to how the Water Department flushes hydrants to clean out water mains, now is the time for you to flush your own system. 

Please contact Water Services if you have any questions at and 705-445-1581

Checklist: Re-Opening Buildings

Map or sketch your entire water system

  • Identify zones and include all treatment equipment, pumps, valves, tanks, etc.
  • List all outlets/fixtures such as taps, fountains, showers, etc.
  • Be sure to include any connected food units like ice or coffee makers  

Flush your entire system

  • Start where the water enters the building and work from closest to furthest, closest zone to furthest zone, closest outlet to furthest outlet
  • Flush at full force by opening the tap fully (remove the aerator filter or shower head) 
  • Flushing requirements vary but run the water until the water maintains a constant cold temperature and the disinfectant (like chlorine) is detected
  • Staff should wear appropriate PPE (gloves, mask, eye cover) while flushing

Hot Water 

  • Flush your cold water system first then your hot water system
  • Hot water should be maintained at a temperature over 50˚C throughout the system.  So the hot water lines need to be flushed and it is highly recommended that, if at all possible, you should drain your hot water tanks and refill
  • Then flush the system from closest to furthest from the tank   


  • Clean, disinfect and rinse all outlets, screens etc. 

Shocking your system

  • Shock chlorination may only need to be considered if you have a large system with isolated branches, storage tanks, or you still detect issues after flushing 
  • Such system shocking should be conducted by a water treatment professional


  • For smaller buildings, after flushing, you should be able to feel a consistent cold temperature and even detect disinfectant (such as chlorine by smell) 
  • For larger buildings and any building serving vulnerable populations, professional testing is highly recommended
  • Testing for disinfectant residual - simple equipment and/or testing services are available from local water treatment companies, plumbers and pool professionals 
  • Testing for microbial diseases – for complex systems, buildings serving vulnerable populations, or any with a history of contaminations (like Legionella) – these issues are often related to water in HVAC systems.  There are products and testing services available – check with your local water treatment company, health unit or utility service for referral