During the COVID-19 pandemic, many buildings, including office buildings, shopping malls, schools, and accommodation providers, have had low or no occupancy for several weeks or months. This reduced water flows in the water system can cause water to stagnate and could promote the growth of disease-causing organisms in the system, including Legionella and Pseudomonas. Water stagnation can also weaken the protective scale on plumbing and allow harmful trace metals like lead to leach into the water system. Not only is this bad for our health, but it can also cause sediment and water discolouration.
Alberta Health Services (AHS) have released a Water Stagnation Fact Sheet to inform building owners and operators of this risk and provide detailed instructions on how to reduce the risks and prepare the building for re-entry.
Solution 105 has summarized some of their instructions, although we strongly recommend your review of the fact sheet to ensure your water systems are healthy as people start to use them again.
Flush the entire system, zone by zone.
Determine which water systems in your building have experienced little to zero use during the pandemic. If you haven’t done so already, you should be flushing these systems regularly to reduce the risks of stagnant water. Some parts of the system will require independent flushing at regular intervals to ensure freshwater is running through the lines. AHS recommends a weekly water-flushing program that completely flushes the endpoints of each floor’s or zone’s cold and hot water supply.
Hot and cold taps should be flushed separately on each floor or zone, starting with the cold water, for at least 5 minutes or until the flow is clear and steady. Start with the zone closest to the water supply following site-specific maintenance procedures or by following the AHS fact sheet provided.
If possible, measure chlorine residuals after flushing, and aim for a residual that is in accordance with your municipal guidelines, as each municipality will have different requirements. Ensure all parts of your system (boilers, HVAC systems, decorative fountains, etc.) are fed freshwater, not stagnant water. If there are any fixtures that do not work well and shouldn’t be used upon re-entry, notify tenants and patrons of the building. However, you could also consider hiring Plumbing services in your vicinity and get it fixed.
Ensure workers are taking safety precautions while flushing the system.
Ensure workers are taking precautions to reduce aerosol exposure when flushing the systems. That means wearing personal protective equipment, including masks, eye protection, and gloves. Some fixtures, like showerheads, for example, will create a risk of hazardous aerosols that could contain disease-causing bacteria like Legionella or Pseudomonas.
Give the water system a thorough inspection.
Inspect all mechanical and plumbing components of the water system. The inspection checklist should include things like boilers, pumps, cooling towers, backflow prevention devices, and fixtures. Check for leaks or depressurization, and ensure everything is functioning correctly. If necessary, you can also consider contacting a Water Damage Property Restoration service to conduct an inspection of the property for any unnoticed water damage.
Inspect and clean heating, ventilation, and cooling systems.
A building’s HVAC system can be a breeding ground for biofilms that support disease-causing bacteria, primarily if they are not used frequently and depend on the water system like air conditioning systems and humidifiers. In many cases, a professional company like CJS Heating & Air will be called to do the honours however, sometimes this can be a DIY job depending on one’s experience and knowledge of the systems.
Check the cooling towers for water stagnation and give the system a thorough cleaning with biocide as per manufacturer’s guidelines. The tower and basin must be free of visible biofilm (slime) before use. You can disinfect it while in use. Find instructions from the Cooling Technology Institute. If the cooling towers need maintenance, contact an HVAC contractor for maintenance and cleaning before use.
Ensure other components of the HVAC system that use water, like humidifiers, are drained and cleaned before use. If any of the parts of the system are not working properly, DUCTZ of Richmond Southside or similar other local service providers could be of assistance and might help in restoring it.
Clean and treat decorative water features.
If your building has a decorative water fountain or feature, it needs to be shut-off, drained, and treated as it could contain harmful residual from stagnant water. Follow manufacturer’s guidelines for cleaning and ensure all water features are free of visible biofilm. When you refill it, ensure there is a minimum total chlorine residual of 0.2mg/L to ensure it’s appropriately disinfected. Refer to the AHS fact sheet for more information.
Recirculate swimming pools and whirlpools.
Swimming pools have also been closed to the public but should have maintained a continuous flow of no less than 75 percent of the design flow rate. Reduced circulation in pools and filter systems can cause stagnant water, causing the growth of harmful bacteria and algae. If you haven’t already, refer to the manufacturer’s instructions regarding shut down or reduced operation. The UK Pool Water Treatment Advisory Group offers guidance for temporary pool closures.
Before anyone uses the pool, proper chlorine and PH levels must be achieved. An AHS public health inspector must inspect the pool and whirlpool before use.
For detailed information on preparing your water system for re-entry, read the AHS Water Stagnation Fact sheet.